Question

Which of the following produces the variance covariance matrix?

(a) sd(x, na.rm=TRUE)

(b) mad(x, na.rm=TRUE)

(c) fivenum(x, na.rm=TRUE)

(d) var(x, na.rm=TRUE)

The question was asked in my homework.

My doubt stems from Commands in chapter Commands, Packages, Visualizing Data and Linear Regression of R Programming

Answer 1

Correct answer is (d) var(x, na.rm=TRUE)

The best explanation: mad(x, na.rm=TRUE) gives median absolute deviation.var(y) instructs R to calculate the sample variance of Y. In other words it uses n-1 ‘degrees of freedom’, where n is the number of observations in Y.sd(y) instructs R to return the sample standard deviation of y, using n-1 degrees of freedom.