OAT Scientific Reading Comprehension 3 — Questions and Answers
Question 1: A passage describes a cohort study following 500 optometry students over 10 years to track myopia progression. The key feature that distinguishes a cohort study from a case-control study is:
- Participants are selected based on exposure status and followed forward in time for outcomes (Correct answer)
- Participants are selected based on whether they already have the disease
- Participants are randomly assigned to treatment or control groups
- The study compares outcomes at a single point in time
Correct answer: Participants are selected based on exposure status and followed forward in time for outcomes
Cohort studies select based on exposure and follow subjects prospectively, whereas case-control studies start with disease status and look backward.
Question 2: A table in a passage shows mean visual acuity values with standard deviations for four age groups. The standard deviation is best interpreted as:
- A measure of spread indicating how much individual values vary around the mean (Correct answer)
- The difference between the highest and lowest values in the group
- The probability that the mean is accurate
- The range within which 95% of values fall
Correct answer: A measure of spread indicating how much individual values vary around the mean
Standard deviation quantifies variability of individual data points around the group mean.
Question 3: A passage introduces a newly coined term 'photoreceptor fatigue index' and defines it in the first paragraph. In subsequent paragraphs, when the author uses this term, the reader should:
- Apply the specific definition provided in the passage, not outside knowledge (Correct answer)
- Use the most common definition from optometry textbooks
- Assume the term refers to photoreceptor damage
- Skip unfamiliar terminology and focus on familiar concepts
Correct answer: Apply the specific definition provided in the passage, not outside knowledge
When a passage defines a technical term, that definition governs its use throughout the passage, regardless of external knowledge.
Question 4: A passage reports: 'Treatment A reduced cup-to-disc ratio by 0.05, while Treatment B reduced it by 0.04 (p = 0.12 for comparison).' The most accurate conclusion is:
- The difference between treatments A and B is not statistically significant (Correct answer)
- Treatment A is clinically superior to Treatment B
- Neither treatment effectively reduced cup-to-disc ratio
- Treatment B is ineffective and should be discontinued
Correct answer: The difference between treatments A and B is not statistically significant
p = 0.12 exceeds the conventional α = 0.05 threshold, meaning the observed difference could plausibly occur by chance.
Question 5: In a passage discussing corneal topography research, the authors state their findings 'may not generalize to pediatric populations.' This caveat addresses which aspect of the study?
- External validity (generalizability) (Correct answer)
- Internal validity (experimental control)
- Statistical power
- Measurement reliability
Correct answer: External validity (generalizability)
External validity concerns whether results can be generalized to populations beyond the study sample.
Question 6: A passage presents a bar graph with error bars representing standard error of the mean (SEM). Overlapping error bars between two groups most likely indicate:
- The difference between group means may not be statistically significant (Correct answer)
- The two groups definitely have the same mean
- The standard deviations are equal across groups
- The sample sizes are identical
Correct answer: The difference between group means may not be statistically significant
Overlapping SEM bars suggest that difference between means may not reach statistical significance, though formal testing is required.
Question 7: A passage describes an experiment where a confounding variable was controlled using 'stratified randomization by age.' The purpose of this technique is to:
- Ensure age is evenly distributed across treatment groups so it cannot explain outcome differences (Correct answer)
- Eliminate older patients from the study to reduce variability
- Increase the sample size by including more age groups
- Analyze age as a primary outcome variable
Correct answer: Ensure age is evenly distributed across treatment groups so it cannot explain outcome differences
Stratified randomization balances potential confounders like age across groups, preventing them from distorting treatment comparisons.
OAT Scientific Reading Comprehension 3
A passage describes a cohort study following 500 optometry students over 10 years to track myopia progression.
The key feature that distinguishes a cohort study from a case-control study is: