Biostatistics & Hypothesis Testing Flashcards

A clinical trial reports a p-value of 0.03 with a pre-specified alpha of 0.05. Which conclusion is most appropriate?

Answer: Reject the null hypothesis

Since p=0.03 < alpha=0.05, the result crosses the pre-specified threshold and the null hypothesis is rejected.

The standard deviation of the sampling distribution of the mean is called the:

Answer: Standard error

The standard error (SE) measures the variability of sample means around the population mean and equals σ/√n.

A researcher uses a two-tailed test instead of a one-tailed test for the same hypothesis. How does this affect the critical region?

Answer: It splits alpha across both tails

A two-tailed test splits alpha (e.g., 0.05) equally into both tails, placing 0.025 in each tail.

Which measure of central tendency is least affected by extreme outliers?

Answer: Median

The median is resistant to outliers because it depends only on the middle value(s), not the magnitude of extreme scores.

In a study with 80% power, what is the probability of committing a Type II error?

Answer: 0.20

Power = 1 − β, so if power is 0.80, the Type II error rate (β) is 1 − 0.80 = 0.20.

A dataset has a mean of 50 and a standard deviation of 10. What is the z-score for an observation of 65?

Answer: 1.5

z = (65 − 50) / 10 = 1.5, indicating the observation is 1.5 standard deviations above the mean.

When comparing means from three or more independent groups in a clinical trial, the preferred initial statistical test is:

Answer: One-way ANOVA

One-way ANOVA is used to test whether at least one group mean differs among three or more independent groups while controlling the overall Type I error rate.