Question

Use R to find the area under Student’s curve with 5 degrees of freedom:

a) to the right of 2.02

b) to the left of -2.02

c) between -2.02 and 2.02

d) to the left of 2.02

Answer 1

The pt( ) function gives the area or probability below a t-value.

a) to find the area the right of 2.02.

> pt(2.02,5)
[1] 0.9503149

above function gives the left-sided area of 2.02.

The area to the right of 2.02 is 1 - 0.9503149 = 0.0497

The area to the right of 2.02 is 0.0497

b) to the left of -2.02 is

> pt(-2.02,5)
[1] 0.04968514
The area to the left of 2.02 is 0.0497

c) between -2.02 and 2.02

to find the two- tailed p value for positive t-value

> 2*(1-pt(2.02,5))
[1] 0.09937029
The area between -2.02 and 2.02 is 0.09937

d) to the left of 2.02 is

> pt(2.02,5)
[1] 0.9503149

The area to the left of 2.02 is 0.9503.