Question

Assume that females have a pulse rates that are normally distributed with a mean of 73.0 beats per minute and a standard deviation of 12.5 beats per minute complete parts a through c.

a. If 1 adult female is randomly selected, find the probablity that her pulse rate is less than 80 beats per minute.

b. If 4 adult females are randomly selected find the probablity that they have pulse rates with a mean less than 80 beats per minute

c. Why can normal distribution be used in part b even though the sample size deos not exceed 30?

Answer 1

a. = 73.0 bpm

= 12.5 bpm

P(X < A) = P(Z < (A - )/)

P(X < 80) = P(Z < (80 - 73)/12.5)

= P(Z < 0.56)

= 0.7123

b. = = 73.0 bpm

n = 4

=

=

= 6.25

P( < A) = P(Z < (A - )/)

P( < 80) = P(Z < (80 - 73/6.25)

= P(Z < 1.12)

= 0.8686

c) We can use normal distribution because here the population distribution is known to be normal. Sample size of 30 or more is required only if the population distribution is not normal.