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Praxis General Science study materials
Praxis General Science study resources

Praxis General Science practice questions

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Question 1Nature and Impact of Science and Engineering

In the scientific method, which statement best describes a hypothesis?

  1. a testable prediction based on prior knowledge Correct answer.
  2. a personal opinion that does not require supporting evidence
  3. a final conclusion that cannot be revised by new evidence
  4. a summary of data collected from many different experiments

Explanation

A hypothesis is a proposed, testable explanation or prediction that is grounded in prior knowledge and can be supported or rejected by evidence. It is not a final conclusion, an unsupported opinion, or a data summary.

Question 2Nature and Impact of Science and Engineering

A student tests how the amount of fertilizer affects the height of bean plants. Which factor is the independent variable?

  1. the type of soil in which the plants are grown
  2. the final height reached by each bean plant
  3. the amount of fertilizer applied Correct answer.
  4. the number of bean plants in each treatment group

Explanation

The independent variable is the factor the experimenter deliberately changes, which here is the amount of fertilizer applied. The height of the plants is the dependent variable that responds to that change.

Question 3Nature and Impact of Science and Engineering

Why is a control group included in a controlled experiment?

  1. to eliminate the need for repeated trials
  2. to increase the number of variables tested
  3. to provide a baseline for comparison Correct answer.
  4. to guarantee that the hypothesis is correct

Explanation

A control group does not receive the treatment and provides a baseline against which the experimental group's results can be compared. This helps isolate the effect of the independent variable.

Question 4Nature and Impact of Science and Engineering

Which SI base unit is used to measure mass?

  1. the joule, a unit of energy
  2. the newton, a unit of force
  3. the kilogram Correct answer.
  4. the liter, a unit of volume

Explanation

The kilogram is the SI base unit of mass. The newton measures force, the liter measures volume, and the joule measures energy.

Question 5Nature and Impact of Science and Engineering

A set of measurements is described as precise but not accurate. Which statement best describes these measurements?

  1. They cluster together but miss the true value. Correct answer.
  2. They cluster tightly around the true value.
  3. They are scattered widely and average near the true value.
  4. They center on the true value but are widely spread.

Explanation

Precision refers to how closely repeated measurements agree with one another, while accuracy refers to how close they are to the true value. Precise but inaccurate measurements are tightly grouped yet offset from the correct value.

Question 6Nature and Impact of Science and Engineering

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

  1. A theory may be revised, while a law is permanent and never changed.
  2. A theory applies only to living things, while a law applies to matter.
  3. A theory explains observations, while a law describes a pattern. Correct answer.
  4. A theory is an initial guess, while a law is an established fact.

Explanation

In science, a theory is a well-supported explanation of observations, while a law is a concise description of a consistent relationship. Both are based on evidence and can be revised if new evidence warrants.

Question 7Nature and Impact of Science and Engineering

What is the main purpose of peer review before a scientific paper is published?

  1. to rewrite the paper so that it is easier for the public to read
  2. to determine how much funding the research should receive
  3. to guarantee that the results will be replicated exactly
  4. to check the work for flaws before it enters the literature Correct answer.

Explanation

Peer review asks independent experts to evaluate a paper's methods, evidence, and reasoning before publication. It is a quality-control step, not a guarantee of replication or funding.

Question 8Nature and Impact of Science and Engineering

In the engineering design process, a constraint is best described as which of the following?

  1. a question that the design team hopes to answer
  2. a limit on what a design is allowed to do Correct answer.
  3. a final product that has passed all tests
  4. a creative idea that has not yet been tested

Explanation

A constraint is a restriction on a design, such as a budget, materials, safety rule, or size limit. Engineers must satisfy constraints while meeting the design's criteria.

Question 9Nature and Impact of Science and Engineering

A researcher wants to test whether a new fertilizer increases crop yield. Which procedure best reduces bias when assigning plants to treatment groups?

  1. randomly assigning plants to treatment groups Correct answer.
  2. letting the researcher choose the healthiest plants
  3. giving fertilizer to every plant and comparing before and after
  4. using only plants grown in one corner of the field

Explanation

Random assignment gives each plant an equal chance of being placed in either group, which helps prevent systematic differences between groups. This reduces bias and makes the comparison fairer.

Question 10Nature and Impact of Science and Engineering

A balance reads 12.30 g. How many significant figures does this measurement have?

  1. five
  2. three
  3. four Correct answer.
  4. two

Explanation

All nonzero digits are significant, and a trailing zero after a decimal point is also significant. The digits 1, 2, 3, and the final 0 therefore give four significant figures.

Question 11Nature and Impact of Science and Engineering

Which of the following is the strongest reason that a claim cannot be considered scientific?

  1. It is supported by only a small number of scientists.
  2. It relies on complex mathematics.
  3. It cannot be tested or shown to be false. Correct answer.
  4. It conflicts with a well-established theory.

Explanation

A scientific claim must be testable and potentially falsifiable by evidence. A claim that cannot be tested or shown false falls outside the scope of scientific investigation.

Question 12Nature and Impact of Science and Engineering

A study finds that towns with more ice-cream sales have more drowning deaths. Which conclusion is most justified?

  1. Ice-cream sales and drowning deaths have no relationship.
  2. An increase in drowning deaths directly raises ice-cream sales.
  3. The variables are correlated but may share a common cause. Correct answer.
  4. Eating ice cream directly increases the risk of drowning.

Explanation

A correlation between two variables does not establish that one causes the other. A third factor, such as warm summer weather, could independently increase both ice-cream sales and swimming, and therefore drowning deaths.

Question 13Nature and Impact of Science and Engineering

A survey about school lunch is mailed only to families who belong to the parent-teacher association. What is the main problem with this sample?

  1. It contains far too many families to analyze properly.
  2. It is biased toward one group of families. Correct answer.
  3. It relies on random selection from the whole district.
  4. It introduces too many independent variables at once.

Explanation

A sample drawn only from PTA members is not representative of all families, because PTA members may differ systematically from other families. This is a form of selection bias that limits how broadly the results can be generalized.

Question 14Nature and Impact of Science and Engineering

Which statement best describes a limitation of using a computer model to predict climate?

  1. Models may only be used after predictions are confirmed.
  2. Models are never based on actual measurements.
  3. Models simplify real systems and carry uncertainty. Correct answer.
  4. Models remove the need for any field observations.

Explanation

Computer models are built from physical principles and data, but they must simplify complex systems and therefore include uncertainty. Their predictions are tested against observations and are not a substitute for field data.

Question 15Nature and Impact of Science and Engineering

After testing a prototype, an engineering team finds that it fails under high heat. What is the next step in the design process?

  1. revise the design and test it again Correct answer.
  2. ignore the failure because the prototype worked once
  3. publish the design without further changes
  4. discard the entire project and start over

Explanation

Engineering design is iterative: test results are used to identify weaknesses, revise the design, and test again. A failure under high heat provides specific information that can guide improvements.

Question 16Nature and Impact of Science and Engineering

A community must decide whether to build a new dam. Which approach best reflects a scientific risk-benefit analysis?

  1. Choose the option that requires the least total money.
  2. Reject the dam because any level of risk is unacceptable.
  3. Choose whichever option the majority prefers without further study.
  4. Weigh expected benefits against the chance and size of harm. Correct answer.

Explanation

Risk-benefit analysis compares the expected advantages of a decision with the probability and severity of possible harms. It uses evidence to inform trade-offs rather than relying only on cost, popularity, or an absolute rejection of risk.

Question 17Nature and Impact of Science and Engineering

Why do scientists place high value on repeating an experiment?

  1. It removes the need to form a hypothesis.
  2. It shows whether results are consistent. Correct answer.
  3. It increases the number of variables studied.
  4. It guarantees that a theory is finally true.

Explanation

Replication checks whether the same procedure produces consistent results, which strengthens confidence in the findings. It does not prove a theory absolutely or eliminate the need for hypotheses.

Question 18Nature and Impact of Science and Engineering

In research involving human participants, informed consent requires which of the following?

  1. written approval from each participant's employer
  2. payment for all of the time spent in the study
  3. a description of risks and the right to withdraw Correct answer.
  4. a guarantee that the experiment will produce positive results

Explanation

Informed consent means participants understand the purpose, procedures, risks, and benefits of a study and voluntarily agree to take part. It also includes the right to withdraw at any time without penalty.

Question 19Nature and Impact of Science and Engineering

A graph shows that as study time increases from 1 to 5 hours, test scores rise and then level off. Which statement best describes the relationship?

  1. Scores decrease steadily as study time increases.
  2. Study time has no measurable effect on test scores.
  3. Scores rise with study time, then level off. Correct answer.
  4. Higher test scores cause students to study more hours.

Explanation

The pattern described is an increase followed by a plateau, which means the benefit of additional study time diminishes after a point. The graph shows an association, not that scores cause study time.

Question 20Nature and Impact of Science and Engineering

When new evidence strongly contradicts a long-accepted scientific explanation, what typically happens?

  1. The evidence is ignored because the explanation is accepted.
  2. The explanation is immediately taught as false in schools.
  3. Scientists stop collecting data on the topic.
  4. The explanation may be revised or replaced after scrutiny. Correct answer.

Explanation

Science is self-correcting: when new evidence conflicts with an accepted explanation, scientists scrutinize the evidence and may revise or replace the explanation. Change usually occurs through careful evaluation rather than immediately.

Question 21Nature and Impact of Science and Engineering

A study reports that students who eat breakfast earn higher grades. Which factor most threatens the conclusion that breakfast causes better grades?

  1. Grades are recorded on a standard numerical scale.
  2. The study included students drawn from several different schools.
  3. Breakfast eaters may also have more stable home routines. Correct answer.
  4. Some students strongly dislike the taste of breakfast foods.

Explanation

A confounding variable is an additional factor that differs between groups and could explain the observed effect. If breakfast eaters also have more stable home routines, those routines rather than breakfast might account for the higher grades.

Question 22Nature and Impact of Science and Engineering

Two groups differ by 2 points, and their 95% confidence intervals overlap substantially. What is the most reasonable interpretation?

  1. The difference is certainly due to the treatment.
  2. The observed difference may be due to chance. Correct answer.
  3. The study proves that no effect exists.
  4. The sample size must have been too small to measure anything.

Explanation

Overlapping confidence intervals indicate that the observed difference is uncertain and could plausibly arise from random variation. The result is therefore not strong evidence of a real treatment effect.

Question 23Nature and Impact of Science and Engineering

Which feature is most characteristic of pseudoscience rather than science?

  1. use of careful quantitative measurements
  2. revision of its claims whenever new data appear
  3. reliance on anecdotes and refusal to be tested Correct answer.
  4. publication in a journal that has editors

Explanation

Pseudoscientific claims often rely on personal stories and resist falsification, shifting their claims when challenged. Science, by contrast, values testable predictions and revises claims in response to data.

Question 24Nature and Impact of Science and Engineering

A study funded by a company finds that its own product is safe. What is the most appropriate response from the scientific community?

  1. Reject the finding because industry funding is always dishonest.
  2. Accept the finding because the company is expert in its product.
  3. Ignore the study and rely on public opinion instead.
  4. Evaluate the methods closely and seek independent replication. Correct answer.

Explanation

A potential conflict of interest warrants closer scrutiny of the study's methods and independent replication, not automatic acceptance or rejection. The evidence, not the funding source alone, should determine the conclusion.

Question 25Nature and Impact of Science and Engineering

A car travels 90 kilometers per hour. What is this speed in meters per second? (1 km = 1000 m; 1 h = 3600 s)

  1. 25 m/s Correct answer.
  2. 54 m/s
  3. 15 m/s
  4. 32 m/s

Explanation

Convert kilometers to meters by multiplying by 1000, and hours to seconds by dividing by 3600. Thus 90 km/h equals 90,000 m / 3600 s = 25 m/s.

Question 26Nature and Impact of Science and Engineering

A student tests how light intensity affects the rate of photosynthesis in Elodea. Which factor is the independent variable?

  1. Light intensity Correct answer.
  2. Rate of photosynthesis
  3. Number of Elodea sprigs
  4. Water temperature

Explanation

The independent variable is the factor intentionally changed by the experimenter; light intensity is varied to observe its effect. The rate of photosynthesis is the dependent variable, and temperature and number of sprigs should be held constant.

Question 27Nature and Impact of Science and Engineering

In a controlled experiment, what is the main purpose of a control group?

  1. To remove the need for repeated trials
  2. To make the hypothesis easier to prove
  3. To increase the total number of participants
  4. To provide a baseline for comparison Correct answer.

Explanation

A control group is not exposed to the treatment being tested, so it shows what would happen without the treatment. Comparing the treatment group with this baseline helps isolate the treatment's effect.

Question 28Nature and Impact of Science and Engineering

How many grams are equivalent to 3.5 kilograms?

  1. 0.0035 g
  2. 35,000 g
  3. 3,500 g Correct answer.
  4. 350 g

Explanation

The prefix kilo- means 1,000, so 1 kg equals 1,000 g. Multiplying 3.5 kg by 1,000 gives 3,500 g.

Question 29Nature and Impact of Science and Engineering

Which SI prefix means one-thousandth of a base unit?

  1. centi
  2. milli Correct answer.
  3. kilo
  4. micro

Explanation

The prefix milli- denotes 10^-3, or one-thousandth. For example, 1 millimeter is one-thousandth of a meter.

Question 30Nature and Impact of Science and Engineering

Which number is expressed correctly in scientific notation?

  1. 4.5 × 10^2 Correct answer.
  2. 0.45 × 10^3
  3. 450 × 10^0
  4. 45 × 10^1

Explanation

Scientific notation writes a number as a coefficient between 1 and 10 multiplied by a power of 10. Only 4.5 × 10^2 meets that form.

Question 31Nature and Impact of Science and Engineering

A student notices that a metal block feels colder than a wooden block at room temperature. Which statement is an inference rather than a direct observation?

  1. The metal conducts heat away from the hand faster. Correct answer.
  2. The wooden block has a rough surface.
  3. Both blocks are in the same room.
  4. The metal block feels colder than the wooden block.

Explanation

An inference is an interpretation or explanation based on observations, while an observation is what is directly sensed. The feeling of coldness is observed, but faster heat conduction is an inferred explanation.

Question 32Nature and Impact of Science and Engineering

A line graph shows how a plant's height changes over several weeks. Which variable belongs on the horizontal axis?

  1. Pot size
  2. Time Correct answer.
  3. Number of leaves
  4. Plant height

Explanation

The horizontal axis usually holds the independent variable, which the experimenter controls or that advances on its own. In this case, time is the independent variable and plant height is the dependent variable.

Question 33Nature and Impact of Science and Engineering

Which observation is quantitative?

  1. The solution mass is 25.0 g. Correct answer.
  2. The solution produced many small bubbles.
  3. The solution changed to a bright blue color.
  4. The solution gave off a strong pungent odor.

Explanation

Quantitative observations involve measurements or numbers, while qualitative observations describe qualities such as color, odor, or bubbling. A mass of 25.0 g is a numerical measurement.

Question 34Nature and Impact of Science and Engineering

A scientist searches only for evidence that supports a favored hypothesis and ignores contradictory data. Which bias does this illustrate?

  1. Selection bias in sampling
  2. Publication bias
  3. Confirmation bias Correct answer.
  4. Observer bias in measurement

Explanation

Confirmation bias is the tendency to seek, interpret, and recall information that confirms existing beliefs while disregarding contrary evidence. The behavior described fits that pattern.

Question 35Nature and Impact of Science and Engineering

In a clinical trial, some participants receive an inactive pill but still report reduced symptoms. This improvement is best described as...

  1. Random measurement error
  2. The placebo effect Correct answer.
  3. A Type I error
  4. The Hawthorne effect

Explanation

The placebo effect is an improvement in symptoms caused by the expectation of treatment rather than by an active ingredient. An inactive pill can produce this response.

Question 36Nature and Impact of Science and Engineering

Why are double-blind procedures used in clinical trials?

  1. To increase the dose of medication given to each participant
  2. To eliminate the need for a separate control group in the trial
  3. To shorten the total duration of the clinical trial
  4. To keep participants and researchers unaware of treatment Correct answer.

Explanation

Double-blinding keeps both participants and researchers from knowing who receives the treatment, reducing expectation and measurement biases. This helps ensure observed effects are due to the treatment.

Question 37Nature and Impact of Science and Engineering

A study reports a correlation coefficient of -0.85 between outdoor temperature and home heating energy use. What does this value indicate?

  1. A strong positive relationship
  2. A strong negative relationship Correct answer.
  3. No relationship between the variables
  4. A weak positive relationship

Explanation

A correlation coefficient ranges from -1 to 1; the sign shows direction and the absolute value shows strength. A value of -0.85 is close to -1, indicating a strong negative relationship.

Question 38Nature and Impact of Science and Engineering

A new teaching method raises average test scores by 1 point, and the result is statistically significant in a very large sample. Which conclusion is most appropriate?

  1. The effect is detectable but practically small. Correct answer.
  2. The method should be rejected as invalid.
  3. The result is probably due to chance.
  4. The method is practically important for every student.

Explanation

Statistical significance means an effect is unlikely to be due to chance under the null hypothesis, not that it is large or important. A 1-point gain may be detectable with a huge sample yet have little practical value.

Question 39Nature and Impact of Science and Engineering

A data set of home prices includes one house priced far above all the others. Which measure of center is most affected by this outlier?

  1. The interquartile range
  2. The mode
  3. The median
  4. The mean Correct answer.

Explanation

The mean uses every value in the data set, so an extreme value can pull it strongly toward the outlier. The median and mode are more resistant to extreme values.

Question 40Nature and Impact of Science and Engineering

Two surveys use the same sampling method, but one includes 50 people and the other includes 500. What is the likely effect of the larger sample?

  1. It guarantees the sample is unbiased.
  2. It gives a more precise estimate. Correct answer.
  3. It eliminates confounding variables.
  4. It makes the results impossible to replicate.

Explanation

Larger samples generally reduce random sampling error, making estimates more precise. They do not automatically remove bias or confounding.

Question 41Nature and Impact of Science and Engineering

A gardener tests whether a new fertilizer affects tomato yield. Which factor should be kept constant across all treatment groups?

  1. Height of the tomato plants
  2. Number of tomatoes produced
  3. Type of fertilizer applied
  4. Amount of sunlight Correct answer.

Explanation

In a fair test, only the independent variable-fertilizer type-should differ among groups. Other factors such as sunlight should be held constant so they do not confound the results.

Question 42Nature and Impact of Science and Engineering

Engineers adjust a computer model of a bridge until its predictions match measurements from a scale model. This process is best called...

  1. Replication
  2. Peer review
  3. Calibration Correct answer.
  4. Random sampling

Explanation

Calibration is the process of tuning a model so its outputs agree with known measurements or observations. This improves confidence in the model's predictions.

Question 43Nature and Impact of Science and Engineering

An engineer selects a lighter but more expensive material for a bicycle frame. This choice best illustrates which aspect of engineering design?

  1. A control group
  2. A scientific law
  3. A trade-off Correct answer.
  4. A repeated trial

Explanation

Engineering design often requires balancing competing criteria, such as weight and cost. Accepting higher cost to gain lower weight is a trade-off.

Question 44Nature and Impact of Science and Engineering

Which approach best evaluates a product's total environmental impact from raw-material extraction through disposal?

  1. A peer review of the product's manual
  2. A survey of the product's price
  3. A life-cycle analysis Correct answer.
  4. A test of the product's colorfastness

Explanation

Life-cycle analysis examines environmental impacts across all stages of a product's life, often called cradle-to-grave. It includes extraction, manufacturing, use, and disposal.

Question 45Nature and Impact of Science and Engineering

Which is a major challenge of relying on solar and wind power for electricity generation?

  1. They cannot be used in any modern power grid.
  2. They release large amounts of carbon dioxide while operating.
  3. Their fuel supply is expected to run out soon.
  4. Their output varies with weather conditions. Correct answer.

Explanation

Solar and wind generation is intermittent because sunlight and wind vary, so output is not constant. Grid operators must manage this variability with storage, backup, or demand flexibility.

Question 46Nature and Impact of Science and Engineering

Which statement best explains why people often perceive involuntary risks, such as radiation from a power plant, as more threatening than voluntary risks, such as driving?

  1. Involuntary risks always cause more deaths than voluntary risks.
  2. Voluntary risks are not studied by scientists.
  3. Radiation from power plants has no possible benefits.
  4. Perceived control and familiarity shape risk perception. Correct answer.

Explanation

Risk perception is influenced by psychological factors, including whether a risk is voluntary, controllable, familiar, or dreaded. People often accept familiar, voluntary risks more readily even when actual mortality rates differ.

Question 47Nature and Impact of Science and Engineering

A toxicologist finds that a chemical causes harm only when exposure exceeds a certain level. This pattern is best described as...

  1. A linear no-threshold response
  2. A placebo response
  3. A correlation coefficient
  4. A threshold dose-response Correct answer.

Explanation

A threshold dose-response means there is an exposure level below which no harmful effect is observed. Above that threshold, harm increases with dose.

Question 48Nature and Impact of Science and Engineering

A study concludes that a drug works when in fact it does not. This is which type of error?

  1. Placebo effect
  2. Type I error Correct answer.
  3. Sampling error
  4. Type II error

Explanation

A Type I error is rejecting a true null hypothesis, which here means finding an effect that is not real. A Type II error is failing to detect a real effect.

Question 49Nature and Impact of Science and Engineering

Which statement best interprets a p-value of 0.03?

  1. The size of the treatment effect is exactly 3%.
  2. Under the null, results this extreme occur 3% of the time. Correct answer.
  3. The result has no practical importance for real-world decisions.
  4. There is a 3% probability that the null hypothesis is actually true.

Explanation

A p-value is the probability of obtaining results at least as extreme as those observed, assuming the null hypothesis is true. It is not the probability that the null is true or a measure of effect size.

Question 50Nature and Impact of Science and Engineering

A graph shows a clear trend between 0 and 10 seconds. A student uses that trend to predict a value at 100 seconds. What is the main risk?

  1. Overfitting the graph's axis labels
  2. Extrapolating beyond the data range Correct answer.
  3. Calculating the mean of the data incorrectly
  4. Using an excessively large number of data points

Explanation

Predicting outside the range of observed data is extrapolation, which assumes the trend continues unchanged. That assumption may fail, especially far beyond the measured range.