ISAT - International Student Admissions Interpreting Scientific Data Questions and Answers — Questions and Answers
Question 1: A researcher is testing the effectiveness of a new drug on reducing high blood pressure. One group of participants receives the new drug, while a second group receives a pill that looks identical but contains no active ingredient. What is the primary purpose of the second group?
- To increase the total number of participants for greater statistical power.
- To act as a control group, providing a baseline to measure the drug's true effect against. (Correct answer)
- To test the side effects of the inactive ingredients used in the pill.
- To ensure that participants in the study have a positive expectation of treatment.
Correct answer: To act as a control group, providing a baseline to measure the drug's true effect against.
The second group, known as a placebo or control group, is crucial in a clinical trial. By comparing the results of the group taking the active drug to the group taking the placebo, researchers can isolate the drug's specific effects from other factors, such as the placebo effect (where patients improve simply because they believe they are receiving treatment) or natural variations in blood pressure.
Question 2: A study finds a strong positive correlation between the number of hours students spend in the library per week and their final exam scores. The authors conclude that spending more time in the library causes higher exam scores. Why might this conclusion be flawed?
- The study should have been conducted over a longer period.
- Correlation does not imply causation; another factor, such as a student's level of motivation, could influence both library time and exam scores. (Correct answer)
- The sample size of the study was likely too small to be significant.
- Final exam scores are not a reliable measure of student learning.
Correct answer: Correlation does not imply causation; another factor, such as a student's level of motivation, could influence both library time and exam scores.
This is a classic example of confusing correlation with causation. While the two variables are related, it's possible a third, unmeasured variable (a confounding variable) is the true cause. For example, highly motivated students are more likely to both spend time in the library and study effectively elsewhere, leading to higher scores. The library time itself might not be the direct cause.
Question 3: The table below shows the results of a clinical trial for a new allergy medication. The data indicates the percentage of patients in different age groups who reported 'significant symptom relief'. | Age Group | Placebo Group Relief | Medication Group Relief | |---|---|---| | 18-35 | 25% | 60% | | 36-55 | 30% | 55% | | 56+ | 28% | 45% | Which statement is the most accurate interpretation of the data?
- The medication is ineffective for patients aged 56 and older.
- The placebo effect was strongest in the 18-35 age group.
- The medication provided the greatest benefit, compared to the placebo, for the 18-35 age group. (Correct answer)
- The medication is less effective as patients get older.
Correct answer: The medication provided the greatest benefit, compared to the placebo, for the 18-35 age group.
To find the medication's benefit, subtract the placebo relief rate from the medication relief rate for each group. For 18-35, the benefit is 60% - 25% = 35%. For 36-55, it's 55% - 30% = 25%. For 56+, it's 45% - 28% = 17%. The largest difference (35%) is in the 18-35 age group, indicating the greatest relative benefit for them.
Question 4: The provided graph shows the population of a certain species of fish in a lake over 10 years, during which a new industrial plant began operations in year 5. The graph shows a steady population from year 1 to 5, followed by a sharp decline from year 6 to 10. Which of the following statements is a valid conclusion based *only* on the data presented?
- The industrial plant is solely responsible for the decline in the fish population.
- The fish population began to decrease after the industrial plant started operations. (Correct answer)
- The lake's ecosystem will not recover from the pollution.
- The fish species will be extinct within another 5 years if the trend continues.
Correct answer: The fish population began to decrease after the industrial plant started operations.
The data shows a temporal relationship: the plant began operations, and then the population declined. This is an observation of correlation in time. However, the graph alone does not provide evidence to prove causation (A), predict the future with certainty (D), or make broad claims about the entire ecosystem's recovery (C). Stating only what the graph shows—that the decrease occurred after the plant opened—is the only fully supported conclusion.
Question 5: A scientist measures the boiling point of pure water at various altitudes. The results are shown in the table below. | Altitude (meters) | Boiling Point (°C) | |---|---| | 0 | 100.0 | | 1000 | 96.7 | | 2000 | 93.4 | | 4000 | 86.8 | Based on the trend in the data, what is the MOST LIKELY boiling point of water at an altitude of 3,000 meters?
- 93.5°C
- 86.7°C
- 90.1°C (Correct answer)
- 91.8°C
Correct answer: 90.1°C
The data shows that the boiling point decreases as altitude increases. The 3,000-meter altitude is exactly halfway between 2,000 meters (93.4°C) and 4,000 meters (86.8°C). To estimate the boiling point at this intermediate altitude (a process called interpolation), one can find the midpoint of the temperatures. The average of 93.4 and 86.8 is (93.4 + 86.8) / 2 = 90.1°C. This is the most logical estimate based on the linear trend between these two points.
Question 6: To investigate the effect of soil pH on tomato plant growth, a student plants five tomato seedlings in identical pots with the same type of soil and gives them the same amount of water and sunlight. The only difference is that the soil for each plant is adjusted to a different pH level (5.0, 5.5, 6.0, 6.5, 7.0). The student measures the final height of each plant after 8 weeks. What is the independent variable in this experiment?
- The final height of the plants.
- The amount of sunlight.
- The pH level of the soil. (Correct answer)
- The type of tomato seedling.
Correct answer: The pH level of the soil.
In a scientific experiment, the independent variable is the one that the experimenter intentionally changes or manipulates to observe its effect on the dependent variable. In this case, the student is deliberately changing the soil pH for each plant to see how it affects growth. The plant's final height is the dependent variable because it is the outcome being measured, which 'depends' on the independent variable.
ISAT - International Student Admissions Interpreting Scientific Data Questions and Answers
A researcher is testing the effectiveness of a new drug on reducing high blood pressure.
One group of participants receives the new drug, while a second group receives a pill that looks identical but contains no active ingredient.
What is the primary purpose of the second group?