R Programming Language Certification Statistical Analysis & Modeling 3

Question 1

What is the purpose of set.seed() in R?

Accepted Answer

Sets a reproducible starting point for random number generation

Answer

set.seed() initializes the random number generator with a fixed value, ensuring reproducible results in simulations and random sampling.

Question 2

Which function computes the mean of a numeric vector, ignoring NA values?

Accepted Answer

mean(x, na.rm=TRUE)

Answer

mean(x, na.rm=TRUE) computes the arithmetic mean of x while excluding NA values from both the numerator and denominator.

Question 3

What does the residuals() function return for a fitted linear model?

Accepted Answer

The difference between observed and fitted values

Answer

residuals() returns the raw residuals (observed minus fitted values) from a fitted model, useful for diagnostic checking.

Question 4

Which function performs k-means clustering in R?

Accepted Answer

kmeans()

Answer

kmeans() partitions data into k clusters by iteratively assigning observations to the nearest centroid and updating centroids.

Question 5

What is the purpose of the scale() function in R?

Accepted Answer

Standardizes numeric variables to mean 0 and standard deviation 1

Answer

scale() centers and standardizes a numeric matrix, by default subtracting the column mean and dividing by the standard deviation.

R Programming Language Certification Practice Test