OAT Scientific Reading Comprehension 5 â Questions and Answers
Question 1: A passage explains that a study used a 'washout period' of two weeks between treatment phases in a crossover design. The purpose of the washout period is to:
- Allow effects of the first treatment to dissipate before starting the second treatment (Correct answer)
- Recruit additional participants between study phases
- Measure baseline values before any treatment begins
- Ensure that researchers are blinded to previous results
Correct answer: Allow effects of the first treatment to dissipate before starting the second treatment
Washout periods in crossover designs prevent carryover effects from the first intervention influencing outcomes in the second phase.
Question 2: A passage presents data showing that 8 out of 100 patients in the treatment group developed dry eye versus 16 out of 100 in the control group. The relative risk reduction is:
- 50% (Correct answer)
- 8%
- 16%
- 24%
Correct answer: 50%
RRR = (control rate - treatment rate) / control rate = (0.16 - 0.08) / 0.16 = 0.50 = 50%.
Question 3: A passage describes a cross-sectional study measuring refractive error and screen time in 1,000 adolescents at a single point in time. A major limitation of this design for establishing causality is:
- Temporal sequence cannot be establishedâit is unknown whether screen time preceded myopia (Correct answer)
- The sample size is too small to detect associations
- Cross-sectional studies cannot measure refractive error accurately
- Adolescents are not a valid population for studying screen time effects
Correct answer: Temporal sequence cannot be establishedâit is unknown whether screen time preceded myopia
Cross-sectional studies measure exposure and outcome simultaneously, making it impossible to determine which came first.
Question 4: A passage notes that after controlling for age, sex, and IOP, the association between corneal hysteresis and glaucoma progression remained significant (OR = 1.8, 95% CI: 1.2â2.6). The fact that CI does not include 1.0 indicates:
- The odds ratio is statistically significant at the 0.05 level (Correct answer)
- The odds ratio is clinically meaningful but not statistically significant
- There is no association between corneal hysteresis and glaucoma progression
- The confidence interval is too wide to draw conclusions
Correct answer: The odds ratio is statistically significant at the 0.05 level
For an odds ratio, a 95% CI that excludes 1.0 indicates statistical significance because 1.0 represents no association.
Question 5: A passage uses the phrase 'the data suggest' rather than 'the data prove.' This language choice reflects:
- Appropriate scientific caution acknowledging that findings support but do not definitively establish conclusions (Correct answer)
- A methodological weakness in the study design
- The authors' uncertainty about their own measurements
- A requirement imposed by the journal's editorial policy
Correct answer: Appropriate scientific caution acknowledging that findings support but do not definitively establish conclusions
Scientific writing uses hedging language like 'suggest' to reflect the probabilistic and provisional nature of empirical evidence.
Question 6: A passage describes a multivariate regression analysis in which visual acuity is the dependent variable. Including multiple independent variables (age, IOP, corneal thickness) in the model primarily allows researchers to:
- Estimate the independent effect of each variable while holding the others constant (Correct answer)
- Prove that each variable directly causes changes in visual acuity
- Eliminate measurement error from each variable
- Identify which single variable is most important to visual acuity
Correct answer: Estimate the independent effect of each variable while holding the others constant
Multivariate regression isolates each variable's contribution by statistically controlling for the effects of all other included variables.
Question 7: A passage presents a scatter plot with a best-fit line showing R² = 0.62 between hours of outdoor activity and axial length. The R² value indicates that:
- 62% of the variance in axial length is explained by hours of outdoor activity (Correct answer)
- The correlation coefficient between the two variables is 0.62
- Outdoor activity causes 62% of all myopia cases
- 62% of participants showed the expected relationship
Correct answer: 62% of the variance in axial length is explained by hours of outdoor activity
R² (coefficient of determination) represents the proportion of variance in the outcome explained by the predictor variable.
OAT Scientific Reading Comprehension 5
A passage explains that a study used a 'washout period' of two weeks between treatment phases in a crossover design.
The purpose of the washout period is to: