Statistics Flashcards

A drug study uses a two-tailed t-test with 20 degrees of freedom at α = 0.05. The critical t-value is approximately 2.086. If the calculated t = 2.5, what is the conclusion?

Answer: Reject the null hypothesis

Since |t| = 2.5 > 2.086 (critical value), the null hypothesis is rejected.

What is the probability of rolling a sum of 7 with two fair six-sided dice?

Answer: 1/6

There are 6 favorable outcomes (1+6, 2+5, 3+4, 4+3, 5+2, 6+1) out of 36 total, so P = 6/36 = 1/6.

A researcher calculates a 90% confidence interval instead of a 95% CI using the same data. How does the width change?

Answer: The interval becomes narrower

Lower confidence levels correspond to smaller critical values, producing narrower confidence intervals.

Which statistical test compares proportions between two independent groups?

Answer: Chi-square test of independence

The chi-square test of independence compares categorical proportions between two or more independent groups.

In hypothesis testing, what does increasing the sample size primarily accomplish?

Answer: Increases statistical power

Larger samples reduce standard error, making it easier to detect true effects and increasing statistical power.

A dataset has values {10, 20, 30, 40, 50}. What is the coefficient of variation (CV)?

Answer: 47.1%

Mean = 30, SD ≈ 15.81; CV = (15.81/30) × 100 ≈ 52.7%, closest to 47.1% among PCAT approximations — SD = √200 ≈ 14.14, CV = 14.14/30 ≈ 47.1%.

Which of the following is a non-parametric alternative to the independent samples t-test?

Answer: Mann-Whitney U test

The Mann-Whitney U test compares two independent groups without assuming normality, making it non-parametric.