ETS Statistical Analysis 4

Question 1

A 95% confidence interval for a population mean is (42, 58). Which interpretation is correct?

Accepted Answer

We are 95% confident the interval (42, 58) captures the true population mean

Answer

Confidence intervals are interpreted as the method capturing the true parameter 95% of the time in repeated sampling, not as probability statements about a fixed mean.

Question 2

Which nonparametric test is the appropriate alternative to the independent samples t-test?

Accepted Answer

Mann-Whitney U test

Answer

The Mann-Whitney U test is the nonparametric equivalent of the independent samples t-test, comparing two independent groups.

Question 3

In a normal distribution, approximately what percentage of data falls within one standard deviation of the mean?

Accepted Answer

68%

Answer

The empirical rule (68-95-99.7 rule) states that approximately 68% of data falls within one standard deviation of the mean in a normal distribution.

Question 4

A researcher uses multiple regression with 4 predictors. The adjusted R² is preferred over R² because it:

Accepted Answer

Penalizes for adding predictors that don't improve the model

Answer

Adjusted R² accounts for the number of predictors, penalizing the addition of variables that do not meaningfully improve model fit.

Question 5

Interquartile range (IQR) is calculated as:

Accepted Answer

Q3 − Q1

Answer

The IQR is the difference between the third quartile (Q3) and the first quartile (Q1), representing the middle 50% of the data.

(ETS) Educational Testing Service Practice Test

(ETS) Educational Testing Service Practice Test

ETS Statistical Analysis 4