Pubh 6330 Biostatistics Completed Exam With Rationales 2024

PUBH 6330 Biostatistics COMPLE TED EXAM w/ RATIONALES 2024 1. Which of the following best defines a p -value in biostatistics? a. The probability that a study result occurred due to chance alone. b. The strength of association between two variables. c. The level of statistical significance required to reject the null hypothesis. d. The confidence interval for an odds ratio. Answer: a. The probability that a study res ult occurred due to chance alone. Rationale: The p -value represents the probability that the observed results (or more extreme) would occur if the null hypothesis were true. It provides evidence for or against the null hypothesis and is used to determine s tatistical significance. 2. A type II error occurs when: a. The null hypothesis is incorrectly rejected. b. The study findings show no significant difference whereas there is one. c. The study sample size is insufficient to detect a true difference. d. Th e p-value is less than 0.05. Answer: b. The study findings show no significant difference whereas there is one. Rationale: A type II error occurs when the null hypothesis is erroneously accepted, leading to the conclusion that there is no significant difference between groups, even though there might be one in reality. 3. When conducting a cross -sectional study, which of the following is the most appropriate measure of association? a. Relative risk (RR) b. Odds ratio (OR) c. Hazard ratio (HR) d. Pears on correlation coefficient (r) Answer: b. Odds ratio (OR) Rationale: Cross -sectional studies examine the relationship between exposures and outcomes at a specific point in time. As such, odds ratios (OR) are commonly used to estimate the association betwe en an exposure and an outcome in this study design. 4. Which statistical test is used to analyze differences between means of two independent groups? a. Student's t -test b. Chi -square test c. Fisher's exact test d. Analysis of variance (ANOVA) Answer: a. Student's t -test Rationale: A Student's t -test is used to compare means between two independent groups, assuming a normal distribution of the variables. 5. In a randomized controlled trial (RCT), which of the following represents the best method to achie ve blinding? a. Participants are oblivious to their assignment. b. Researchers are aware of which group participants belong to. c. Only the statistical analyst is blinded to the group assignments. d. Researchers and participants are both blinded to group a ssignments. Answer: d. Researchers and participants are both blinded to group assignments. Rationale: Blinding in an RCT refers to concealing treatment allocation from both researchers and participants to minimize bias. This helps ensure that the assessme nt of outcomes remains objective. 6. Which statistical test is most appropriate to assess the relationship between two categorical variables? a. Linear regression b. Spearman's rank correlation coefficient c. Chi -square test d. Analysis of covariance (ANCOVA) Answer: c. Chi -square test Rationale: The chi -square test assesses the association between two categorical variables based on observed and expected frequencies. It is commonly used to determine if there is a significant relationship between the two variables.