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MTTC Earth/Space Science (020) study materials
MTTC Earth/Space Science (020) study resources

MTTC Earth/Space Science (020) practice questions

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Question 1Foundations of Scientific Inquiry

A scientist hypothesizes that a certain mineral's cleavage pattern is caused by weak planes in its crystal lattice. Which statement best describes this hypothesis in the context of scientific inquiry?

  1. It is a proven law because it explains an observed phenomenon.
  2. It is a testable proposed explanation that can be supported or refuted by observations of many mineral samples. Correct answer.
  3. It is a theory because it has not yet been tested against data.
  4. It is an observation because it describes the mineral's cleavage directly.

Explanation

A hypothesis is a testable, tentative explanation that must be evaluated against evidence. Observing cleavage in many samples and comparing lattice structure could support or refute it, so it is not yet a law or theory.

Question 2Foundations of Scientific Inquiry

A student measures the density of four basalt samples and gets 2.91, 2.89, 2.90, and 2.92 g/cm³. The accepted value is 3.01 g/cm³. Which description best fits these results?

  1. Accurate but not precise
  2. Both accurate and precise
  3. Neither accurate nor precise
  4. Precise but not accurate Correct answer.

Explanation

Precision concerns how closely repeated measurements agree with one another, while accuracy concerns closeness to the accepted value. The four values cluster tightly together but all lie well below 3.01 g/cm³, so they are precise but inaccurate, suggesting a systematic error.

Question 3Foundations of Scientific Inquiry

In an experiment on soil erosion, a student varies the slope angle of a soil tray while keeping soil type, water volume, and flow rate constant. Which variable is the independent variable?

  1. Volume of water applied
  2. Amount of soil eroded
  3. Soil type
  4. Slope angle of the tray Correct answer.

Explanation

The independent variable is the factor the experimenter deliberately changes, which here is the slope angle. The amount of eroded soil is the dependent variable, while water volume and soil type are controlled variables.

Question 4Foundations of Scientific Inquiry

Which statement correctly distinguishes a scientific theory from a scientific law?

  1. A theory becomes a law once enough evidence accumulates.
  2. A law explains underlying mechanisms, whereas a theory only summarizes observations.
  3. A theory is a guess, whereas a law is a confirmed fact.
  4. A theory explains why phenomena occur, whereas a law describes a consistent relationship among phenomena. Correct answer.

Explanation

In science, theories are well-supported explanatory frameworks, while laws are concise descriptions of consistent relationships. They serve different roles and one does not convert into the other as evidence accumulates.

Question 5Foundations of Scientific Inquiry

A rock sample's mass is recorded as 24.6 g using a balance readable to 0.1 g. Which statement about this measurement is correct?

  1. It has four significant figures.
  2. It is more precise than a balance readable to 0.01 g.
  3. The trailing digit 6 is not significant.
  4. The reported value implies uncertainty of about ±0.1 g. Correct answer.

Explanation

The last recorded digit reflects the instrument's readability, so a balance readable to 0.1 g gives uncertainty of roughly ±0.1 g. All three digits are significant, and a balance readable to 0.01 g would be more precise.

Question 6Foundations of Scientific Inquiry

Which practice is most important for ensuring that a measurement of atmospheric pressure can be reproduced by other scientists?

  1. Rounding the result to the nearest whole number
  2. Ignoring readings that differ from the expected value
  3. Recording the instrument type, units, and conditions of measurement Correct answer.
  4. Reporting only the single highest reading

Explanation

Reproducibility depends on documenting exactly how and under what conditions a measurement was made, including the instrument, units, and environment. Discarding data or reporting only extremes undermines the integrity of the record.

Question 7Foundations of Scientific Inquiry

In a controlled study of plant growth under different light colors, which feature most strengthens the study's internal validity?

  1. Using a single plant for each light color
  2. Measuring growth only at the final harvest
  3. Randomly assigning many plants to each treatment group Correct answer.
  4. Having the researcher who designed the study also guess the results

Explanation

Random assignment of many subjects to treatments reduces bias and averages out uncontrolled differences, strengthening internal validity. Single subjects and infrequent measurements increase the influence of chance variation.

Question 8Foundations of Scientific Inquiry

Which of the following is the best example of a qualitative observation in an Earth science investigation?

  1. The water temperature is 18 °C.
  2. The sample mass is 340 g.
  3. The sandstone has rounded, frosted grains. Correct answer.
  4. The sandstone sample is 12 cm long.

Explanation

Qualitative observations describe properties or qualities without numerical measurement, such as grain shape and texture. Length, temperature, and mass are quantitative because they are expressed as numbers with units.

Question 9Foundations of Scientific Inquiry

A geologist repeatedly measures the strike of a rock layer and obtains values of 45°, 46°, 44°, 45°, and 45°. Which conclusion is best supported?

  1. The measurements contain a large systematic error.
  2. The measurements are highly precise, suggesting low random error. Correct answer.
  3. The measurements are invalid because they are too similar.
  4. The measurements are accurate but imprecise.

Explanation

Closely clustered repeated measurements indicate high precision and low random error. Accuracy and systematic error cannot be assessed without an independent accepted value, and similarity among readings is not a flaw.

Question 10Foundations of Scientific Inquiry

A student wants to test whether the type of bedrock affects the pH of groundwater. Which design best isolates the effect of bedrock type?

  1. Sample groundwater from sites with different bedrock but similar climate, depth, and soil cover Correct answer.
  2. Measure the pH of rainwater instead of groundwater
  3. Sample only one site and measure pH repeatedly
  4. Sample groundwater from many sites with varied climate, depth, and bedrock

Explanation

To isolate bedrock as the cause, other factors that influence groundwater pH must be held as similar as possible. Varying climate, depth, and soil cover would confound the comparison, and rainwater is not groundwater.

Question 11Foundations of Scientific Inquiry

A scientist predicts that a newly discovered sedimentary layer will contain fossils of marine organisms. Fieldwork confirms the prediction. What is the most appropriate scientific conclusion?

  1. The hypothesis is refuted because only one prediction was tested.
  2. The hypothesis is now a scientific law.
  3. The hypothesis is proven true and requires no further testing.
  4. The hypothesis is supported, but not proven, because it may be tested further. Correct answer.

Explanation

Confirming a prediction supports a hypothesis but does not prove it, since future evidence could still challenge it. Scientific conclusions remain provisional and are strengthened by repeated independent testing.

Question 12Foundations of Scientific Inquiry

Which change would most improve the reliability of a study measuring stream discharge?

  1. Using a single measurement at one site
  2. Changing the measurement method at each site
  3. Taking repeated measurements at each site and averaging them Correct answer.
  4. Recording only the values that match the expected discharge

Explanation

Reliability improves when repeated measurements are taken and averaged, reducing the influence of random variation. Inconsistent methods and selective recording introduce bias and reduce trustworthiness.

Question 13Foundations of Scientific Inquiry

An Earth science model simulates plate motion over millions of years. Which criterion is most important for evaluating the model's usefulness?

  1. Whether it matches the researcher's original intuition
  2. Whether it uses the most advanced computer available
  3. Whether it reproduces observed patterns and makes testable predictions Correct answer.
  4. Whether it is simple enough to explain in one sentence

Explanation

A scientific model is judged by how well it accounts for observed data and by whether it generates predictions that can be tested. Simplicity, intuition, and computing power do not by themselves establish a model's validity.

Question 14Foundations of Scientific Inquiry

A researcher reports a correlation between sunspot activity and average global temperature but questions whether one causes the other. Which statement best reflects appropriate scientific reasoning?

  1. Correlation proves causation when the data span many years.
  2. Correlation alone does not establish causation; alternative explanations must be evaluated. Correct answer.
  3. Causation can be assumed if the correlation coefficient is high.
  4. The correlation must be ignored because it involves two complex systems.

Explanation

Correlation indicates that variables vary together but does not by itself demonstrate that one causes the other. Researchers must consider confounding factors and mechanisms before inferring causation.

Question 15Foundations of Scientific Inquiry

Which unit and instrument pairing is most appropriate for measuring the mass of a mineral specimen in a school laboratory?

  1. Newtons measured with a graduated cylinder
  2. Liters measured with a balance
  3. Degrees Celsius measured with a spring scale
  4. Grams measured with an electronic balance Correct answer.

Explanation

Mass is measured in grams using a balance, which compares the specimen to known masses. Newtons measure force, liters measure volume, and degrees Celsius measure temperature, each requiring different instruments.

Question 16Foundations of Scientific Inquiry

A student's experiment shows that iron-rich rocks heat more quickly in sunlight than quartz-rich rocks. Which additional step would best test whether iron content causes the difference?

  1. Compare rocks of similar size and shape that differ only in iron content Correct answer.
  2. Measure the rocks' color instead of their temperature
  3. Compare rocks of different sizes and iron contents
  4. Repeat the test on the same two rocks many times

Explanation

To test causation, the rocks must be matched on other variables such as size and shape so that iron content is the only difference. Varying multiple factors or merely repeating the same comparison does not isolate the cause.

Question 17Foundations of Scientific Inquiry

Which statement about peer review in Earth science publication is most accurate?

  1. It guarantees that published results are free of error.
  2. It replaces the need for replication by other scientists.
  3. It is performed only by the authors of the paper.
  4. It provides independent expert scrutiny before publication but does not guarantee the findings are correct. Correct answer.

Explanation

Peer review subjects a manuscript to evaluation by independent experts, improving quality and catching problems before publication. It cannot guarantee correctness, and replication remains essential.

Question 18Foundations of Scientific Inquiry

A scientist uses a computer model to forecast coastal erosion. The model's output closely matches observed erosion over the past decade. Which statement best evaluates this result?

  1. The model is proven correct for all future conditions.
  2. The model is invalid because it relies on computers.
  3. The model needs no further testing because it matched past data.
  4. Agreement with past observations supports the model but does not guarantee accurate future predictions. Correct answer.

Explanation

A model that reproduces past observations gains support, but future conditions may differ from those used to build it. Continued testing and validation under varied conditions are necessary before relying on forecasts.

Question 19Foundations of Scientific Inquiry

A team publishes a study concluding that a certain rock formation is 200 million years old. Which action would most directly test the reproducibility of this conclusion?

  1. Reading the original paper more carefully
  2. Citing the study in a textbook
  3. An independent laboratory dating samples from the same formation using the same method Correct answer.
  4. Increasing the sample size in the original study's figure

Explanation

Reproducibility involves independent investigators obtaining comparable results using the same or equivalent methods. Reading, citing, or altering figures does not independently verify the original measurement.

Question 20Foundations of Scientific Inquiry

Which of the following best illustrates the use of a control group in an Earth science investigation?

  1. Measuring the same plot before and after a treatment with no untreated comparison
  2. Testing only the treated plot to save time
  3. Changing several conditions between two plots
  4. Comparing a treated soil plot with an untreated plot under otherwise identical conditions Correct answer.

Explanation

A control group provides a baseline against which the effect of a treatment can be measured. Without an untreated comparison under otherwise identical conditions, changes cannot be confidently attributed to the treatment.

Question 21Foundations of Scientific Inquiry

A researcher samples mineral composition at 10 randomly chosen sites across a large lava flow. Why is random sampling preferable to choosing sites near the researcher's camp?

  1. Random sampling guarantees that every site has identical composition.
  2. Random sampling eliminates the need for multiple measurements.
  3. Random sampling ensures the results will match a previous study.
  4. Random sampling reduces selection bias and better represents the whole flow. Correct answer.

Explanation

Random selection gives every part of the flow a chance of being sampled, reducing bias and improving representativeness. It does not guarantee uniformity or agreement with prior work, and replication remains valuable.

Question 22Foundations of Scientific Inquiry

Two studies estimate the age of a rock unit. Study A reports 250 ± 2 million years; Study B reports 250 ± 20 million years. Which statement is most defensible?

  1. The two studies cannot be compared because their uncertainties differ.
  2. Study B is more accurate because it has a larger uncertainty.
  3. Study A must be wrong because its uncertainty is small.
  4. Study A's estimate is more precise, though both may be accurate if they agree with independent evidence. Correct answer.

Explanation

A smaller uncertainty indicates greater precision, not necessarily greater accuracy. Both estimates could be accurate if they are consistent with independent evidence, and they can be compared directly.

Question 23Foundations of Scientific Inquiry

A geologist proposes that a certain fossil assemblage indicates a warm, shallow marine environment. Which finding would most seriously weaken this interpretation?

  1. Evidence that the fossils were transported and deposited in deep, cold water Correct answer.
  2. Confirmation that the fossils are well preserved
  3. Discovery that the rock layer is thicker than expected
  4. Additional fossils of the same types found nearby

Explanation

An interpretation is weakened by evidence that the fossils do not reflect their original environment of life. Transport and deposition in deep, cold water would undermine the warm, shallow marine inference.

Question 24Foundations of Scientific Inquiry

A scientist's hypothesis predicts a specific result, but the experiment yields a different one. What is the most appropriate scientific response?

  1. Repeat the experiment until the predicted result appears
  2. Reclassify the hypothesis as a law to preserve it
  3. Revise or reject the hypothesis and consider alternative explanations consistent with the data Correct answer.
  4. Discard the data because they contradict the hypothesis

Explanation

Scientific inquiry requires that hypotheses yield to evidence, so unexpected results prompt revision or rejection of the hypothesis. Discarding data or repeating until a desired result appears violates scientific integrity.

Question 25Foundations of Scientific Inquiry

A team claims that a new method detects trace metals in groundwater more reliably than the standard method. Which evidence would most strongly support this claim?

  1. A description of the new method's design without comparative data
  2. A single test in which the new method gave a higher reading
  3. Blinded trials on many samples showing lower variability and closer agreement with known concentrations Correct answer.
  4. A statement by the method's inventor that it works better

Explanation

Claims of superior reliability require comparative, replicated evidence, ideally with blinding, showing lower variability and better agreement with known values. Single tests, design descriptions, and inventor testimony are insufficient.

Question 26Foundations of Scientific Inquiry

A student measures the length of a mineral crystal five times and records 4.2, 4.3, 4.1, 4.2, and 6.9 cm. The value 6.9 cm differs sharply from the others. Which term best describes this single value in the context of the data set?

  1. An outlier Correct answer.
  2. A calibration standard
  3. A control variable
  4. A systematic error

Explanation

An outlier is a data point that lies far from the general pattern of the other measurements and may indicate a recording mistake or an unusual event. It is identified by its distance from the cluster, not by any assumption about its cause.

Question 27Foundations of Scientific Inquiry

Which statement correctly distinguishes a scientific hypothesis from a scientific theory?

  1. A hypothesis is always correct once tested, while a theory remains an untested guess.
  2. A hypothesis is a proven law, while a theory is a preliminary idea awaiting confirmation.
  3. A hypothesis applies only to laboratory work, while a theory applies only to field observations.
  4. A hypothesis is a testable proposed explanation, while a theory is a broad explanation well supported by extensive evidence. Correct answer.

Explanation

In science, a hypothesis is a testable, tentative explanation for a specific observation, whereas a theory is a comprehensive framework supported by many lines of evidence. The everyday use of "theory" as a mere guess does not match its scientific meaning.

Question 28Foundations of Scientific Inquiry

A seismograph records ground motion, and a scientist reports that a tremor had a magnitude of 4.5. Which characteristic of this statement makes it a quantitative observation?

  1. It was recorded during the night.
  2. It includes a numerical value obtained with an instrument. Correct answer.
  3. It describes the shaking as frightening to residents.
  4. It was reported by a single observer.

Explanation

Quantitative observations involve measurements expressed as numbers with units, here a magnitude value from a seismograph. Qualitative observations instead describe qualities such as color, texture, or apparent intensity without numerical measurement.

Question 29Foundations of Scientific Inquiry

In the International System of Units, which base unit is used to express the amount of a substance in a sample of rock or water?

  1. The kelvin
  2. The mole Correct answer.
  3. The candela
  4. The ampere

Explanation

The mole is the SI base unit for amount of substance, defined by a fixed number of elementary entities. It is distinct from units of temperature, luminous intensity, and electric current.

Question 30Foundations of Scientific Inquiry

A student wants to determine the density of a rock sample. Which pair of measurements is required?

  1. Volume and color
  2. Mass and temperature
  3. Mass and volume Correct answer.
  4. Hardness and luster

Explanation

Density is mass divided by volume, so both quantities must be measured to compute it. Temperature, color, hardness, and luster do not enter the density calculation.

Question 31Foundations of Scientific Inquiry

Which practice best supports the reproducibility of an Earth science investigation?

  1. Publishing conclusions before the data are analyzed
  2. Reporting only the results that match the original hypothesis
  3. Recording the procedures, instruments, and conditions in enough detail for another scientist to repeat them Correct answer.
  4. Rounding all measurements to the nearest whole number

Explanation

Reproducibility requires that others can repeat the work and obtain comparable results, which depends on transparent documentation of methods, instruments, and conditions. Selective reporting or premature conclusions undermines scientific credibility.

Question 32Foundations of Scientific Inquiry

A scientist wants to communicate that repeated measurements of a mineral's hardness cluster tightly around the same value. Which term describes this characteristic?

  1. Significance
  2. Precision Correct answer.
  3. Accuracy
  4. Validity

Explanation

Precision refers to how closely repeated measurements agree with one another, regardless of whether they match the true value. Accuracy instead describes closeness to the accepted or true value.

Question 33Foundations of Scientific Inquiry

A geologist uses a hand lens to examine a rock and notes that it contains visible grains of two different colors. Which type of observation has the geologist made?

  1. Experimental
  2. Statistical
  3. Quantitative
  4. Qualitative Correct answer.

Explanation

Noting the presence and colors of grains is a qualitative observation because it describes qualities rather than measured numerical values. Quantitative observations would include measured grain sizes or percentages.

Question 34Foundations of Scientific Inquiry

A researcher wants to test whether the mineral composition of bedrock affects the pH of groundwater. Which design best isolates the effect of bedrock composition?

  1. Collect groundwater samples from wells in areas where only the bedrock composition differs and other conditions are similar Correct answer.
  2. Measure the pH of a single well repeatedly over one day
  3. Collect groundwater samples from many wells chosen without regard to bedrock type
  4. Compare groundwater pH with the pH of nearby rainwater only

Explanation

To isolate bedrock composition as the cause, other variables such as climate, depth, and land use should be held as similar as possible while bedrock varies. This allows differences in pH to be attributed to the bedrock rather than confounding factors.

Question 35Foundations of Scientific Inquiry

A student measures the same water sample with a pH meter three times and obtains 7.1, 7.1, and 7.1, but a calibrated reference electrode shows the true pH is 8.1. Which statement best describes the student's measurements?

  1. They are both accurate and precise.
  2. They are precise but not accurate. Correct answer.
  3. They are accurate but not precise.
  4. They are neither precise nor accurate.

Explanation

Precision describes how closely repeated measurements agree, and these three values are nearly identical, so they are precise. Accuracy describes closeness to the true value, and a consistent offset of one pH unit shows a systematic error, making them inaccurate.

Question 36Foundations of Scientific Inquiry

A scientist proposes that a particular sandstone layer was deposited in a high-energy river environment. Which observation would provide the strongest independent support for this hypothesis?

  1. The sandstone contains large, rounded pebbles and cross-bedding consistent with fast-flowing water Correct answer.
  2. The sandstone is tan in color and occurs near a road
  3. The sandstone layer is the thickest in the region
  4. The sandstone was sampled by two different geologists

Explanation

Sedimentary structures and grain characteristics such as large rounded clasts and cross-bedding are direct evidence of the energy and flow conditions during deposition. Supporting a hypothesis requires evidence specifically linked to the proposed process.

Question 37Foundations of Scientific Inquiry

A researcher studying coastal erosion wants to ensure that a sample of beach profiles represents the entire shoreline. Which sampling approach best reduces bias?

  1. Choosing profile locations near the most accessible parking areas
  2. Measuring only the profiles that show the most dramatic change
  3. Selecting profile locations randomly across the full length of the shoreline Correct answer.
  4. Selecting profiles based on the researcher's prior expectations

Explanation

Random selection across the full extent of the shoreline gives every location a chance of being sampled, reducing the chance that the sample reflects only convenient or unusual sites. Convenience or expectation-based selection introduces bias.

Question 38Foundations of Scientific Inquiry

A team reports that a new spectrometer detects trace arsenic in groundwater more reliably than the standard method. Which evidence would most strongly support this claim?

  1. The new spectrometer is smaller and less expensive than the standard instrument
  2. Replicate analyses of known standards show the new method has lower measurement uncertainty than the standard method Correct answer.
  3. The new method produces results in less time than the standard method
  4. The team prefers the software interface of the new instrument

Explanation

Reliability refers to consistency and low measurement uncertainty, which can be demonstrated by replicate analyses of standards with known concentrations. Cost, speed, and user preference are practical advantages but do not establish measurement reliability.

Question 39Foundations of Scientific Inquiry

A scientist uses a computer model to predict the path of a lava flow. Which action would best test the model's validity?

  1. Adding more colors to the model's output display
  2. Comparing the model's predictions with the observed paths of past lava flows Correct answer.
  3. Increasing the number of times the model is run
  4. Running the model on a faster computer

Explanation

A model is validated by comparing its predictions with independent observations of real events. Computational speed, display features, and repeated runs do not test whether the model's output matches reality.

Question 40Foundations of Scientific Inquiry

Two scientists independently analyze the same seismic data set and reach the same conclusion. Which aspect of scientific practice does this most directly illustrate?

  1. Peer review
  2. Replication of analysis Correct answer.
  3. Instrument calibration
  4. Hypothesis generation

Explanation

Replication occurs when independent investigators analyze data or repeat an investigation and obtain consistent results, which strengthens confidence in the conclusion. Peer review is a separate process of critical evaluation before publication.

Question 41Foundations of Scientific Inquiry

A scientist's hypothesis predicts that a certain rock unit will be magnetic, but field measurements show it is not. What is the most appropriate next step?

  1. Change the hypothesis after the data are reported without disclosure
  2. Revise or reject the hypothesis and investigate alternative explanations for the observations Correct answer.
  3. Report the prediction as confirmed to preserve the hypothesis
  4. Discard the measurements because they contradict the hypothesis

Explanation

When data conflict with a prediction, the hypothesis must be revised or rejected, and alternative explanations should be explored. Discarding valid data or misreporting results violates scientific integrity.

Question 42Foundations of Scientific Inquiry

A scientist wants to determine whether a correlation between solar activity and global temperature reflects causation. Which additional evidence would most strengthen a causal claim?

  1. A public statement by a prominent scientist endorsing the link
  2. A second data set showing the same correlation over the same period
  3. A longer graph showing both variables with matching peaks
  4. A plausible physical mechanism linking solar activity to temperature change, supported by independent data Correct answer.

Explanation

Correlation alone does not establish causation; a credible physical mechanism supported by independent evidence strengthens a causal interpretation. Repeating the correlation or citing authority does not rule out confounding factors.

Question 43Foundations of Scientific Inquiry

A researcher reports a radiometric age of 250 ± 2 million years for a rock unit. Which statement best interprets the reported uncertainty?

  1. The measurement is invalid because it includes an uncertainty
  2. The rock is exactly 250 million years old with no possible error
  3. The true age is likely close to 250 million years, with about 2 million years representing the estimated analytical uncertainty Correct answer.
  4. The uncertainty means the age could be anywhere from 0 to 500 million years

Explanation

A reported value with uncertainty indicates a best estimate plus a range reflecting measurement and analytical variability. The uncertainty quantifies confidence in the estimate rather than invalidating the result.

Question 44Foundations of Scientific Inquiry

A student wants to compare the permeability of two soil samples. Which procedure best controls variables so that permeability differences can be attributed to the samples?

  1. Testing one sample in a wide container and the other in a narrow tube
  2. Using different water volumes for each sample to save time
  3. Testing each sample only once
  4. Packing each sample to the same bulk density and applying the same water volume and head Correct answer.

Explanation

Permeability depends on both the material and conditions such as packing and hydraulic head, so these must be held constant to isolate the effect of the sample. Consistent procedures and replication improve the comparison.

Question 45Foundations of Scientific Inquiry

A geologist finds that two rock layers contain the same index fossil species. Which conclusion is best supported by this observation?

  1. The two layers formed at exactly the same location
  2. The two layers must have identical mineral compositions
  3. The two layers were likely deposited during the same limited interval of geologic time Correct answer.
  4. The two layers are the same age to the nearest year

Explanation

Index fossils are species with wide geographic distribution and short stratigraphic ranges, so their presence in two layers suggests correlation within the same time interval. It does not imply identical composition, location, or year-level age.

Question 46Foundations of Scientific Inquiry

A researcher claims that a new field kit measures soil nitrate concentrations as accurately as a laboratory method. Which evidence would best evaluate this claim?

  1. The field kit's faster readout time
  2. Paired measurements of the same soil samples by both methods, compared against known nitrate standards Correct answer.
  3. The number of field kits sold to schools
  4. The field kit's lower purchase price

Explanation

Accuracy is evaluated by comparing the new method's results with an established reference or known standards on the same samples. Cost, speed, and popularity are practical attributes that do not establish accuracy.

Question 47Foundations of Scientific Inquiry

A scientist studying groundwater flow builds a physical scale model using sand and dye. Which limitation most directly affects the model's ability to represent a real aquifer?

  1. The model is photographed during the experiment
  2. The model is built in a transparent container
  3. The model uses colored dye that is easy to see
  4. The model simplifies the heterogeneous structure and slow timescale of a real aquifer Correct answer.

Explanation

Scale models necessarily simplify real systems, and differences in heterogeneity, scale, and time can limit how well results transfer to nature. Visibility aids observation but does not itself limit representation.

Question 48Foundations of Scientific Inquiry

A team reports that a rock formation is 200 million years old based on one radiometric date from a single mineral separate. Which action would most directly strengthen the conclusion?

  1. Reporting the age without stating the analytical uncertainty
  2. Publishing the result before independent review
  3. Obtaining concordant ages from multiple independent mineral separates and methods Correct answer.
  4. Selecting only the mineral separate that gives the youngest age

Explanation

Concordant ages from multiple independent minerals and methods reduce the chance that the result reflects contamination, inheritance, or analytical error. Skipping review or omitting uncertainty weakens rather than strengthens a conclusion.

Question 49Foundations of Scientific Inquiry

A scientist proposes that a mass extinction was caused by a large asteroid impact. Which combination of findings would provide the strongest independent support for this hypothesis?

  1. A worldwide iridium anomaly at the extinction boundary together with a buried crater of matching age Correct answer.
  2. A computer model that assumes an impact occurred
  3. A single local layer containing unusual clay minerals
  4. A newspaper report describing the impact

Explanation

Independent lines of evidence, such as a global geochemical anomaly and a crater of matching age, converge to support the impact hypothesis. A single local observation, a news report, or a model built on the assumption cannot provide comparable independent support.

Question 50Foundations of Scientific Inquiry

Two laboratories date the same volcanic ash layer. Laboratory A reports 66.0 ± 0.5 million years, and Laboratory B reports 66.2 ± 0.4 million years. Which conclusion is best supported?

  1. The results contradict each other because the central values differ
  2. Laboratory B's result must be wrong because its uncertainty is smaller
  3. The age of the ash layer cannot be determined
  4. The two results overlap within their uncertainties and are consistent with each other Correct answer.

Explanation

When reported ranges overlap, the measurements are statistically consistent even if the central values differ slightly. Comparing uncertainties properly requires examining whether the ranges overlap rather than whether the central values are identical.