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

Initializes a new data frame

Answer

Seeds a database connection

Answer

Defines the random sampling distribution

Question 2

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

Accepted Answer

mean(x, na.rm=TRUE)

Answer

mean(x)

Answer

mean(x, na.rm=FALSE)

Answer

mean_clean(x)

Question 3

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

Accepted Answer

The difference between observed and fitted values

Answer

Predicted values

Answer

Standardized coefficients

Answer

Cook's distance values

Question 4

Which function performs k-means clustering in R?

Accepted Answer

kmeans()

Answer

cluster.k()

Answer

kclust()

Answer

hclust()

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

Rescales a plot axis

Answer

Converts ordinal data to interval

Answer

Adjusts p-values for multiple testing

Question 6

Which function in R computes the variance of a numeric vector?

Accepted Answer

var()

Answer

std()

Answer

sd()^2 only

Answer

variance()