CRA Biostatistics & Hypothesis Testing 2

Question 1

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

Accepted Answer

Reject the null hypothesis

Answer

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

Question 2

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

Accepted Answer

Standard error

Answer

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

Question 3

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

Accepted Answer

It splits alpha across both tails

Answer

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

Question 4

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

Accepted Answer

Median

Answer

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

Question 5

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

Accepted Answer

0.20

Answer

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

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