Question

The mean number of words per minute (WPM) typed by a speed typist is 123 with a standard deviation of 14 WPM. What is the probability that the sample mean would differ from the population mean by more than 1 WPM if 52 speed typists are randomly selected? Round your answer to four decimal places.

Answer 1

Solution :

Given that,

mean = = 123

standard deviation = = 14

= / n = 14 / 52 = 1.9415

= 1 - P[(-1) / 1.9415< ( - ) / < (1) / 1.9415)]

= 1 - P(-0.52 < Z < 0.52)

= 1 - P(Z < 0.52) - P(Z < -0.52)

= 1 - P(0.6985 - 0.3015)

= 1 - 0.397

= 0.6030

Probability = 0.6030