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HSC Investigating Science practice questions

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Question 1Scientific Investigations

A student writes a hypothesis before beginning an experiment. Which statement best describes the main purpose of a hypothesis in a scientific investigation?

  1. It guarantees the experiment will produce accurate results
  2. It summarises the final conclusions of the investigation
  3. It lists the safety precautions needed during the practical work
  4. It provides a testable prediction that can be supported or refuted by evidence Correct answer.

Explanation

A hypothesis is a proposed explanation or prediction framed so that observations can test it. Evidence gathered during the investigation may support or refute it, and it is never a guarantee of a correct outcome. It is stated before data collection, not after conclusions are drawn.

Question 2Scientific Investigations

In a controlled experiment, which variable is deliberately changed by the investigator?

  1. The independent variable Correct answer.
  2. The dependent variable
  3. The confounding variable
  4. The controlled variable

Explanation

The independent variable is the factor the investigator manipulates on purpose to observe its effect. The dependent variable is the measured response, while controlled variables are kept constant to ensure a fair test. A confounding variable is an unintended factor that may distort results.

Question 3Scientific Investigations

A student repeats a measurement five times and obtains very similar values, but the true value is known to be quite different. Which statement best describes these measurements?

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

Explanation

Precision refers to how closely repeated measurements agree with each other, while accuracy refers to how close they are to the true value. Consistent values that cluster away from the true value are precise but inaccurate, often due to systematic error. Random error would instead spread the values widely.

Question 4Scientific Investigations

Which of the following is the best example of a primary source of scientific data?

  1. Raw measurements recorded by a student during their own experiment Correct answer.
  2. A review article comparing results from many laboratories
  3. A news article reporting on a published discovery
  4. A textbook chapter summarising several studies

Explanation

Primary data are collected first-hand by the investigator through their own observations or measurements. Secondary sources interpret, summarise or report on data gathered by others, such as textbooks, news reports and review articles. Raw measurements recorded directly during an experiment are therefore primary.

Question 5Scientific Investigations

A student tests how light intensity affects the rate of photosynthesis in pond weed. Which is the most appropriate dependent variable?

  1. The distance of the lamp from the plant
  2. The number of oxygen bubbles produced per minute Correct answer.
  3. The species of aquatic plant used
  4. The temperature of the water bath

Explanation

The dependent variable is the response that is measured, here the rate of photosynthesis estimated by counting oxygen bubbles per minute. The lamp distance is the independent variable being changed, and temperature and plant species are controlled variables kept constant.

Question 6Scientific Investigations

Which piece of equipment is most suitable for measuring the volume of a liquid accurately in a school laboratory?

  1. A measuring cylinder Correct answer.
  2. A beaker
  3. A test tube
  4. A conical flask

Explanation

A measuring cylinder has a graduated scale designed for measuring liquid volumes with reasonable accuracy. Beakers, conical flasks and test tubes are marked only approximately and are intended for holding or mixing liquids. For accurate volume measurement, a graduated instrument such as a measuring cylinder is chosen.

Question 7Scientific Investigations

Why should a scientific investigation include a control group?

  1. To increase the total number of measurements taken
  2. To ensure the experiment finishes more quickly
  3. To provide a baseline for comparison so the effect of the independent variable can be judged Correct answer.
  4. To allow the investigator to change several variables at once

Explanation

A control group is treated identically to the experimental group except that it does not receive the independent variable. Comparing results against this baseline helps show whether the treatment actually caused the observed effect. It is not about speed or sample size, and it does not permit changing multiple variables.

Question 8Scientific Investigations

A student records the mass of a sample as 12.4 g, 12.5 g and 12.4 g using a balance. Which term best describes the closeness of these repeated readings to one another?

  1. Reliability Correct answer.
  2. Accuracy
  3. Validity
  4. Resolution

Explanation

Reliability describes how consistent repeated measurements are when the procedure is repeated. Closely agreeing readings indicate high reliability. Accuracy concerns closeness to the true value, validity concerns whether the method measures the intended quantity, and resolution is the smallest change an instrument can detect.

Question 9Scientific Investigations

A student wants to investigate whether fertiliser concentration affects the growth of bean plants. Which combination best represents a controlled variable and a suitable control treatment?

  1. Controlled variable: amount of water given; control treatment: plants given no fertiliser Correct answer.
  2. Controlled variable: number of leaves; control treatment: plants measured twice daily
  3. Controlled variable: plant height; control treatment: plants grown in darkness
  4. Controlled variable: fertiliser concentration; control treatment: plants given the highest fertiliser dose

Explanation

A controlled variable is kept constant across all groups, such as the volume of water given. A control treatment provides a baseline without the independent variable, so plants receiving no fertiliser serve this role. The other pairs confuse the independent variable, dependent variable or measurement schedule with these roles.

Question 10Scientific Investigations

During a titration, a student consistently reads the burette from above eye level rather than at eye level. What type of error does this introduce?

  1. No error, because the reading method does not affect results
  2. A systematic error that shifts all readings in the same direction Correct answer.
  3. A random error that varies unpredictably between trials
  4. A sampling error caused by an unrepresentative sample

Explanation

Parallax from viewing the meniscus from above eye level shifts every reading in the same direction, producing a systematic error. Systematic errors reduce accuracy consistently rather than scattering results randomly. Random errors, by contrast, vary unpredictably in both directions between trials.

Question 11Scientific Investigations

A student measures the extension of a spring for increasing hanging masses and plots a line of best fit. Several points lie well off the line. What is the most appropriate action?

  1. Repeat the measurements for the anomalous points and check for procedural mistakes Correct answer.
  2. Draw the line to pass through every data point regardless of scatter
  3. Remove all points that do not fit and redraw the line through the remaining points
  4. Change the hypothesis so that it matches the anomalous points

Explanation

Anomalous points may result from measurement or procedural errors, so the sound approach is to recheck and repeat those readings. Selectively deleting inconvenient data without justification is unacceptable. A line of best fit should reflect the overall trend rather than be forced through every point.

Question 12Scientific Investigations

A student tests a new fertiliser on 30 plants in one garden bed and compares them with 30 plants in a different bed that receives a different amount of sunlight. What is the main weakness of this design?

  1. The dependent variable was not measured
  2. Sunlight differs between groups, so it is a confounding variable Correct answer.
  3. The sample size is too small to draw any conclusion
  4. Fertiliser cannot be tested on plants

Explanation

A valid comparison requires that groups differ only in the independent variable. If one bed receives more sunlight, any difference in growth could be due to light rather than fertiliser, making sunlight a confounding variable. The design flaw is the lack of control over this factor, not the sample size alone.

Question 13Scientific Investigations

Which statement best explains why scientific findings are peer reviewed before publication?

  1. To have independent experts check the methods, evidence and reasoning for quality Correct answer.
  2. To ensure the research receives government funding
  3. To guarantee that the results will never be challenged
  4. To allow the authors to promote their work to the public

Explanation

Peer review involves independent experts in the field evaluating the methods, evidence and interpretation before publication. It improves quality and filters weak or flawed work, but it does not guarantee that findings are correct or unchallengeable. Promotion and funding are unrelated to the review process.

Question 14Scientific Investigations

A student claims that a plant grew taller because they played music to it, based on a single plant that grew 2 cm more than a neighbour. Which improvement would most strengthen the investigation?

  1. Measure the plant only once at the end
  2. Play the music more loudly to the same plant
  3. Use more plants per group and keep all other conditions identical Correct answer.
  4. Use a different type of plant for each group

Explanation

Increasing the number of plants per group reduces the influence of individual variation and improves reliability. Keeping all other conditions identical ensures the only difference is the music, supporting a valid causal claim. A single plant provides no basis for separating treatment effects from natural variation.

Question 15Scientific Investigations

A graph of temperature against time for a cooling substance shows a curve. Which statement best describes how a line of best fit should be used?

  1. It should show the overall trend of the data while accounting for scatter Correct answer.
  2. It should be drawn only through the first and last points
  3. It should ignore the axes and follow the steepest section
  4. It should connect every plotted point exactly in sequence

Explanation

A line of best fit represents the overall trend of the data, balancing points above and below the line. It does not need to pass through every point, because measurement scatter is expected. Connecting all points exactly produces a jagged line that obscures the underlying relationship.

Question 16Scientific Investigations

In an investigation, a student reports a measurement as 25.0 cm with an uncertainty of plus or minus 0.5 cm. What does this uncertainty indicate?

  1. The student made a mistake during the measurement
  2. The measurement likely lies between 24.5 cm and 25.5 cm Correct answer.
  3. The true value is exactly 25.0 cm
  4. The instrument cannot measure beyond 25.0 cm

Explanation

An uncertainty of plus or minus 0.5 cm means the measured value could reasonably fall within 0.5 cm either side of the reading. It reflects the limits of the instrument and technique, not a specific error or a maximum reading. The true value is therefore likely between 24.5 cm and 25.5 cm.

Question 17Scientific Investigations

A scientist repeats an experiment using a different method and obtains results consistent with the original study. Which concept does this best illustrate?

  1. Subjectivity of observation
  2. Random error
  3. Reproducibility of results Correct answer.
  4. Lack of validity

Explanation

Reproducibility is demonstrated when independent investigators using a different method obtain consistent results. This strengthens confidence that the findings reflect a real phenomenon rather than one method's artefact. Random error and subjectivity would tend to produce inconsistent outcomes instead.

Question 18Scientific Investigations

A student investigates how the concentration of acid affects the rate of reaction with marble chips. They use chips of different sizes across trials. What is the most likely effect on the investigation?

  1. It improves validity because more conditions are varied
  2. It introduces a confounding variable that may affect the rate Correct answer.
  3. It increases the reliability of the results
  4. It has no effect because surface area is unrelated to reaction rate

Explanation

Surface area affects reaction rate, so varying chip size alongside acid concentration introduces a confounding variable. Any change in rate could then be due to either factor, reducing validity. Only the independent variable should differ between trials.

Question 19Scientific Investigations

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

  1. A law applies only to physics, while a theory applies only to biology
  2. A law is proven, while a theory is merely a guess
  3. A theory is always replaced by a law once enough data are collected
  4. A law describes a consistent relationship, while a theory explains why that relationship occurs Correct answer.

Explanation

A scientific law typically describes a consistent, repeatable relationship between observed quantities. A theory is a well-supported explanatory framework accounting for why such relationships occur. Theories are not mere guesses, and they are not automatically replaced by laws as data accumulate.

Question 20Scientific Investigations

A student writes: 'If the temperature of water increases, then sugar will dissolve faster.' Which feature makes this a useful hypothesis for investigation?

  1. It has already been proven correct by other students
  2. It cannot be tested using school equipment
  3. It states a clear, testable relationship between two measurable variables Correct answer.
  4. It includes several variables that change together

Explanation

A useful hypothesis predicts a specific relationship between measurable variables that can be tested with data. Here temperature and dissolving time are both measurable, allowing the prediction to be supported or refuted. Being untestable or involving several changing variables would weaken it.

Question 21Scientific Investigations

A team of scientists publishes a study showing a correlation between screen time and poor sleep in adolescents. Which conclusion is most justified from a correlational study alone?

  1. Reducing screen time will definitely improve sleep
  2. Screen time has no relationship with sleep quality
  3. There is an association, but causation requires further controlled investigation Correct answer.
  4. Poor sleep causes adolescents to use screens more, which is proven

Explanation

Correlational studies show that two variables are associated but cannot establish which causes which, or rule out other factors. Concluding causation requires controlled experiments or stronger evidence. The data support an association, not a definite causal direction.

Question 22Scientific Investigations

A pharmaceutical trial randomly assigns participants to a treatment group or a placebo group, and neither participants nor assessors know who receives which. Which statement best describes why this design is strong?

  1. Randomisation and blinding reduce bias and help isolate the treatment effect Correct answer.
  2. It allows the researchers to choose which participants receive the treatment
  3. It removes the need for any statistical analysis
  4. It guarantees that every participant will improve

Explanation

Random assignment balances known and unknown confounding factors between groups. Blinding prevents participants' expectations and assessors' biases from influencing outcomes. Together these features help isolate the true treatment effect, though they do not guarantee improvement or remove the need for analysis.

Question 23Scientific Investigations

A student's experiment yields results that contradict their hypothesis. What is the most scientifically appropriate response?

  1. Report the results honestly and consider whether the hypothesis or method needs revision Correct answer.
  2. Abandon the investigation and choose a new topic
  3. State that the experiment must have failed despite careful checks
  4. Adjust the raw data so they support the hypothesis

Explanation

Scientific investigation accepts that evidence may not support a hypothesis, and honest reporting is essential. The appropriate response is to analyse whether the method was sound and to revise the hypothesis in light of evidence. Manipulating data or dismissing valid results undermines scientific integrity.

Question 24Scientific Investigations

Two laboratories measure the same standard reference sample. Lab A obtains values tightly clustered around a value 10 percent too high, while Lab B obtains widely scattered values whose average is very close to the true value. Which statement best compares them?

  1. Lab A is imprecise but accurate; Lab B is precise but inaccurate
  2. Lab A is precise but inaccurate; Lab B is relatively accurate on average but imprecise Correct answer.
  3. Both laboratories are equally accurate and precise
  4. Lab A is accurate and precise; Lab B is neither accurate nor precise

Explanation

Lab A's tightly clustered but displaced readings indicate a systematic error, giving high precision but poor accuracy. Lab B's scattered readings average near the true value, indicating reasonable accuracy but low precision. Precision and accuracy are independent properties, so a method can be high in one and low in the other.

Question 25Scientific Investigations

A researcher finds that a new drug reduces symptoms in a sample, with a p-value of 0.04. Which interpretation is most appropriate?

  1. The result proves the drug is effective for the whole population
  2. There is about a 4 percent probability of obtaining such a result if no real effect existed Correct answer.
  3. The drug has no effect because the p-value is above 0.01
  4. There is a 96 percent chance the drug will work in every patient

Explanation

A p-value estimates the probability of observing results at least as extreme as those obtained if the null hypothesis were true. A value of 0.04 suggests such a result would be unlikely under no effect, supporting a real association. It does not prove effectiveness for every individual or the whole population.

Question 26Scientific Investigations

In a scientific investigation, what is the main purpose of stating a hypothesis before collecting data?

  1. To summarise the final conclusions of the investigation
  2. To list the safety equipment required for the procedure
  3. To guarantee that the experiment will produce the expected outcome
  4. To provide a testable prediction that can be supported or refuted by the results Correct answer.

Explanation

A hypothesis is a proposed explanation or prediction framed so that evidence can test it. Stating it in advance keeps the investigation focused and allows results to be judged against a clear claim rather than adjusted after the fact.

Question 27Scientific Investigations

A student wants to test whether light intensity affects the rate of photosynthesis in pond weed. Which variable should be deliberately changed?

  1. The number of bubbles counted per minute
  2. The temperature of the water
  3. The distance of the lamp from the plant Correct answer.
  4. The volume of water in the beaker

Explanation

The independent variable is the factor the investigator deliberately manipulates. Changing the lamp distance alters light intensity, which is the factor under test, while other conditions should be held constant.

Question 28Scientific Investigations

Which of the following best describes the dependent variable in an experiment?

  1. The factor that the investigator deliberately changes
  2. The factor that is kept constant throughout the investigation
  3. The factor that is measured in response to changes Correct answer.
  4. The factor that is assumed to have no effect

Explanation

The dependent variable is the outcome measured in the investigation; its value is expected to depend on the independent variable. Controlled variables, by contrast, are kept fixed to prevent confounding.

Question 29Scientific Investigations

Why is it important to record raw data directly in a laboratory notebook during an investigation?

  1. It proves the hypothesis was correct
  2. It allows data to be altered later to better fit the hypothesis
  3. It provides an original, dated record that can be checked and verified Correct answer.
  4. It removes the need to repeat measurements

Explanation

Raw data recorded at the time provide an authentic, traceable record that others can audit. This supports reproducibility and integrity, and it prevents later accidental or deliberate distortion of results.

Question 30Scientific Investigations

A student uses a ruler marked in millimetres to measure the length of a leaf. Which statement about the measurement is most accurate?

  1. The measurement should be reported to the nearest centimetre
  2. The measurement has zero uncertainty because the ruler is calibrated
  3. The measurement has a resolution of 1 mm and should be reported to the nearest millimetre Correct answer.
  4. The measurement is exact because rulers are precise instruments

Explanation

Resolution is the smallest scale division an instrument can read, which here is 1 mm. Measurements are reported to that resolution, with an associated reading uncertainty of roughly half a division.

Question 31Scientific Investigations

Which action best improves the reliability of an experiment's results?

  1. Changing the method between trials
  2. Increasing the sample size of a single trial only
  3. Repeating the measurement several times and averaging the values Correct answer.
  4. Using a more expensive piece of equipment

Explanation

Reliability concerns consistency of results when the investigation is repeated. Repeating measurements and averaging reduces the influence of random variation and gives a more dependable value.

Question 32Scientific Investigations

A scientist wants to determine whether a new fertiliser increases crop yield. Which approach best supports a valid conclusion?

  1. Ask farmers whether they believe the fertiliser works
  2. Apply the fertiliser to one half of a field and no fertiliser to the other half, with all other conditions the same Correct answer.
  3. Apply the fertiliser to the whole field and compare with last year's harvest
  4. Apply the fertiliser and record the yield without any comparison

Explanation

A valid causal conclusion requires a comparison group that differs only in the factor being tested. Treating half the field and leaving the other half untreated, with all else equal, isolates the fertiliser's effect.

Question 33Scientific Investigations

Which statement best defines a scientific model?

  1. A final conclusion that ends further research
  2. A proven fact that cannot be revised
  3. A guess made without any evidence
  4. A simplified representation used to explain or predict aspects of a real system Correct answer.

Explanation

Models are deliberate simplifications of complex systems, used to explain observations and make predictions. Because they are simplified, they are always open to revision as evidence improves.

Question 34Scientific Investigations

A student measures the boiling point of a liquid three times and obtains 78.2, 78.3 and 78.2 degrees Celsius, while the accepted value is 78.4 degrees Celsius. How should these results be described?

  1. Both imprecise and inaccurate
  2. Precise but with a small systematic error Correct answer.
  3. Accurate but imprecise
  4. Neither precise nor accurate

Explanation

Precision refers to how closely repeated values agree with each other, and these values cluster tightly. Accuracy refers to closeness to the true value; the small consistent offset from 78.4 indicates a systematic bias rather than random scatter.

Question 35Scientific Investigations

A student investigates whether the concentration of salt solution affects the mass of potato chips. Which is the most appropriate control setup?

  1. A potato chip left on the bench for the same time
  2. A second chip in a higher salt concentration
  3. A potato chip placed in distilled water under the same conditions Correct answer.
  4. A chip weighed only at the end of the experiment

Explanation

A control provides a baseline against which the effect of the independent variable can be judged. Distilled water contains no salt, so it isolates the effect of salt concentration while keeping all other conditions constant.

Question 36Scientific Investigations

A student's graph of reaction rate against temperature shows points curving upward. Which action would best test whether the relationship is genuinely non-linear?

  1. Drawing a straight line through the origin regardless of the points
  2. Removing the points that do not fit the curve
  3. Collecting more data points across the range of temperatures Correct answer.
  4. Averaging all the rate values into a single number

Explanation

More data across the range allow the shape of the relationship to be assessed with greater confidence. With sparse points, apparent curvature could reflect scatter rather than a real trend.

Question 37Scientific Investigations

A scientist reports a result as 5.2 plus or minus 0.3 units. Which statement best interprets this?

  1. The measurement lies in the range 4.9 to 5.5 units with a stated level of confidence Correct answer.
  2. The true value is exactly 5.2 units
  3. The measurement is wrong by 0.3 units
  4. The instrument cannot measure below 5.5 units

Explanation

A plus-or-minus value expresses the uncertainty attached to a measurement. It indicates a range within which the true value is expected to lie, typically at a stated confidence level.

Question 38Scientific Investigations

In a double-blind clinical trial, why is it important that neither the participants nor the researchers know who receives the treatment?

  1. To eliminate the need for a control group
  2. To reduce bias from expectations influencing the reported outcomes Correct answer.
  3. To ensure every participant receives the active treatment
  4. To make the trial cheaper to run

Explanation

Expectations can influence both participants' reported symptoms and researchers' assessments. Blinding both parties reduces this source of bias, making the comparison between groups fairer.

Question 39Scientific Investigations

A student claims that a new study guide improves exam marks because students who bought the guide scored higher than those who did not. Which is the most serious flaw in this reasoning?

  1. Students who buy a study guide may already be more motivated, confounding the result Correct answer.
  2. Marks are not a valid measure of learning
  3. The study did not use a computer
  4. The sample size may be too large

Explanation

The comparison groups differ in motivation as well as in guide use, so any difference in marks cannot be attributed to the guide alone. This is a confounding variable that undermines a causal claim.

Question 40Scientific Investigations

Which statement best describes the role of a risk assessment in planning a scientific investigation?

  1. It replaces the need for ethical approval
  2. It identifies hazards and the controls needed to reduce harm before work begins Correct answer.
  3. It is only needed for investigations involving chemicals
  4. It guarantees that no accidents will occur

Explanation

A risk assessment systematically identifies hazards, evaluates the likelihood and severity of harm, and specifies controls. It is a planning tool that reduces risk rather than a guarantee of safety.

Question 41Scientific Investigations

A scientist repeats an experiment using a different method and obtains results consistent with the original study. Which conclusion is best supported?

  1. The original results are more likely to be valid because they are reproducible across methods Correct answer.
  2. The second method is automatically superior
  3. The original results must be wrong because the method changed
  4. The findings are now proven beyond any doubt

Explanation

Reproduction by an independent method strengthens confidence because agreement is unlikely to arise from a flaw specific to one procedure. Science never reaches absolute proof, but consistency across methods supports validity.

Question 42Scientific Investigations

A student plots data and finds that as one variable increases, the other also increases consistently. Which statement is justified?

  1. The relationship must be linear
  2. One variable definitely causes the other to change
  3. A positive correlation exists between the two variables Correct answer.
  4. The data are unreliable

Explanation

A consistent increase in one variable alongside another describes a positive correlation. Correlation alone does not establish causation, because a third factor could influence both variables.

Question 43Scientific Investigations

A student writes a method that another student cannot follow because steps are missing. Which change would most improve the reproducibility of the method?

  1. Describing the conclusion in more detail
  2. Removing the hypothesis to save space
  3. Including exact quantities, equipment and step order Correct answer.
  4. Adding more results tables

Explanation

Reproducibility requires that another investigator can repeat the procedure exactly. Specifying quantities, equipment and the sequence of steps removes ambiguity and allows independent replication.

Question 44Scientific Investigations

A scientist uses a random number generator to assign participants to treatment groups. What is the main purpose of this step?

  1. To ensure the groups are as similar as possible on unknown factors Correct answer.
  2. To allow the researcher to choose the most suitable participants
  3. To make the experiment shorter
  4. To guarantee the treatment will work

Explanation

Random assignment distributes both known and unknown characteristics evenly across groups. This reduces systematic differences between groups, so any effect observed is more likely due to the treatment.

Question 45Scientific Investigations

A graph shows a strong correlation between ice-cream sales and rates of sunburn. Which explanation is most consistent with scientific reasoning?

  1. Sunburn causes people to buy ice cream
  2. Hot sunny weather increases both ice-cream sales and sun exposure Correct answer.
  3. The correlation is proof of a direct causal link
  4. Eating ice cream causes sunburn

Explanation

A third variable, hot sunny weather, plausibly drives both increased ice-cream purchases and greater sun exposure. This confounding factor explains the correlation without any direct causal link between the two observed variables.

Question 46Scientific Investigations

A student wants to compare the effectiveness of two antacid tablets. They crush one tablet and use a whole tablet of the other brand. Why does this design limit the validity of the comparison?

  1. Crushing tablets always makes them ineffective
  2. The experiment lacks a dependent variable
  3. Validity depends only on the number of trials
  4. The brands differ in both identity and surface area, so the cause of any difference is ambiguous Correct answer.

Explanation

A valid comparison should vary only the factor under test. Here brand and surface area change together, so any difference in reaction cannot be attributed to brand alone.

Question 47Scientific Investigations

Two investigations measure the same quantity. Study A reports 10.0 plus or minus 0.1 units; Study B reports 10.0 plus or minus 1.0 unit. Which statement is most appropriate?

  1. Both studies have identical precision
  2. Study A's estimate is more precise, but both could be accurate Correct answer.
  3. Study A must be inaccurate because its uncertainty is smaller
  4. Study B's estimate is more precise because its uncertainty is larger

Explanation

A smaller uncertainty indicates a more precise estimate, meaning repeated values would cluster more tightly. Precision does not by itself guarantee accuracy, so both estimates could still be close to the true value.

Question 48Scientific Investigations

A researcher reports that a treatment produced a statistically significant improvement with a very small effect size. Which interpretation is most appropriate?

  1. The result must be due to a calculation error
  2. Statistical significance proves the treatment works for every patient
  3. The improvement is unlikely to be due to chance, but its practical importance may be limited Correct answer.
  4. The treatment is guaranteed to be highly effective in practice

Explanation

Statistical significance indicates that an observed difference is unlikely under the null hypothesis. Effect size, however, describes the magnitude of the difference, and a small effect may have little practical value.

Question 49Scientific Investigations

A team proposes a new theory that explains existing data and predicts a previously unobserved phenomenon. Which outcome would most strongly support the theory?

  1. The original data are re-analysed using the same method
  2. The theory is complex and difficult to understand
  3. The predicted phenomenon is later observed in an independent experiment Correct answer.
  4. The theory becomes popular on social media

Explanation

A risky, novel prediction confirmed by independent observation provides strong support because the result could easily have refuted the theory. Re-analysing the same data does not provide independent evidence.

Question 50Scientific Investigations

An investigation finds a difference between two groups with a p-value of 0.20. Which conclusion is most appropriate?

  1. The observed difference could plausibly be due to chance, so the evidence is inconclusive Correct answer.
  2. The null hypothesis is proven true
  3. The sample size must have been too small to measure anything
  4. The treatment is proven to be ineffective

Explanation

A p-value of 0.20 means a difference at least this large would occur by chance about one time in five if there were no real effect. This is not strong evidence against the null hypothesis, so the result is inconclusive rather than proof of no effect.