ISAT Interpreting Scientific Data 4 — Questions and Answers
Question 1: A clinical trial uses a double-blind design. What is the primary purpose of keeping both participants and researchers unaware of group assignments?
- To reduce the sample size needed
- To eliminate the placebo effect entirely
- To prevent bias from influencing results or reporting (Correct answer)
- To make data collection faster
Correct answer: To prevent bias from influencing results or reporting
Double-blind design prevents both participant expectation (placebo effect) and researcher bias from skewing data collection and interpretation.
Question 2: A table of experimental results shows: Trial 1: 45 g, Trial 2: 46 g, Trial 3: 44 g, Trial 4: 89 g. What should a scientist do with Trial 4 before reporting results?
- Include it because all data must be reported
- Average it in with the other trials
- Investigate it as a potential outlier before deciding whether to include it (Correct answer)
- Discard it automatically since it differs from the others
Correct answer: Investigate it as a potential outlier before deciding whether to include it
An anomalous result should be investigated for experimental error before deciding to include or exclude it, not automatically discarded.
Question 3: A graph displays the half-life decay of Carbon-14. After 3 half-lives (approximately 17,190 years), what fraction of the original Carbon-14 remains?
- 1/2
- 1/4
- 1/6
- 1/8 (Correct answer)
Correct answer: 1/8
After each half-life, half the remaining material decays: after 3 half-lives, (1/2)³ = 1/8 of the original amount remains.
Question 4: A researcher plots data and calculates a line of best fit with equation y = 3x + 5. If x represents hours of study and y represents test score, what score does the model predict for 4 hours of study?
- 12
- 17 (Correct answer)
- 20
- 23
Correct answer: 17
Substituting x = 4: y = 3(4) + 5 = 12 + 5 = 17.
Question 5: A bar graph compares average annual income across four occupations. Error bars are shown on each bar. Two bars' error bars overlap significantly. What does this overlap suggest?
- The two occupations have identical incomes
- The difference in average income between the two occupations may not be statistically significant (Correct answer)
- The data was collected incorrectly
- The sample sizes were too large
Correct answer: The difference in average income between the two occupations may not be statistically significant
Overlapping error bars (often representing standard error or confidence intervals) suggest the observed difference may be within the range of sampling variability.
Question 6: An experiment measures the melting point of an unknown substance five times: 83°C, 84°C, 83°C, 85°C, 83°C. What is the mode of these measurements?
- 83°C (Correct answer)
- 83.6°C
- 84°C
- 85°C
Correct answer: 83°C
The mode is the most frequently occurring value; 83°C appears three times, more than any other value.
Question 7: A Venn diagram shows that 30 students study biology, 25 study chemistry, and 10 study both. How many students study biology or chemistry (or both)?
- 35
- 45 (Correct answer)
- 55
- 65
Correct answer: 45
Using the inclusion-exclusion principle: 30 + 25 − 10 = 45 students study at least one of the two subjects.
ISAT Interpreting Scientific Data 4
A clinical trial uses a double-blind design.
What is the primary purpose of keeping both participants and researchers unaware of group assignments?