R Programming Language Certification Research & Evidence-Based Practice 2

Question 1

Which R function is used to perform a paired t-test when comparing before-and-after measurements on the same subjects?

Accepted Answer

t.test(x, y, paired = TRUE)

Answer

Setting paired = TRUE in t.test() tells R the two vectors are matched pairs from the same subjects.

Question 2

In R, what does the `set.seed()` function ensure in a research context?

Accepted Answer

Reproducibility of random number generation

Answer

set.seed() initializes the random number generator to a fixed state, ensuring the same 'random' results on every run.

Question 3

A researcher uses `lm(outcome ~ predictor, data = df)` in R. What does this fit?

Accepted Answer

A simple linear regression model

Answer

lm() fits a linear model; with one predictor this is simple linear regression.

Question 4

Which R package provides the `tidy()` function to convert model outputs into clean data frames suitable for reporting?

Accepted Answer

broom

Answer

The broom package's tidy() function converts statistical model objects into tidy data frames.

Question 5

What is the purpose of `confint()` in R when evaluating a regression model?

Accepted Answer

Calculate confidence intervals for model parameters

Answer

confint() returns confidence intervals for the estimated coefficients of a fitted model.

R Programming Language Certification Practice Test