Probability

Question

The distribution of the width of a standard piece of computer paper is normal with an expectation of 8.5 inches and the standard deviation of 0.2 inch.

 

a) Find the probability that the width of any given piece of computer paper is between 8.40 and 8.55.

b) Find the probability that the width of any given piece of computer paper is less than 8.35.

c) Find the probability that the width of any given piece of computer paper is greater than 8.6.

Answer 1

The process here is to find the mean, std dev, calculate the z value(s) and find the probability.

 

a) 8.4 is (8.4-8.5)/.2=-.5 std dev's away. 8.55 is 8.55-8.5/2=2.5.

P(Z<=2.5)-P(Z<=-.5)=

b) 8.35 is 8.35-8.5/.2=.75std dev's away so P(Z<=-.75)

c) 8.6 is 8.6-8.5/.2=.5 std dev's away or 1-P(Z<=.5)

 

Hope that helps,

Deanna