Question

A simple random sample of size n = 20 is obtained from a population with population mean 64 and population standard deviation 17.

(a) What must be true regarding the distribution of the population in order to use the
normal model to compute probabilities involving the sample mean? Assuming that
the condition is true, describe the sampling distribution of sample mean.
(b) Find P(x < 67.3).
(c) Find P(x > 65.2).

Answer 1

Kindly check explanation

0.57691

0.4719

Explanation

A.) The distribution of sample means must follow a normal distribution ;

Mean = 64 ; Standard deviation = 17 ;

Standard Error = s/sqrt(n) = 17 / sqrt(20) = 3.8013155

N(64 ~ 17)

Given that:

mean (m) = 64

Sample size (n) = 20

Standard deviation (s) = 17

Find

P(x < 67.3)

Z = (x - m) / s

Zscore = (67.3 - 64) / 17

Zscore = 0.1941176

P(Z < 0.194) = 0.57691 (Z probability calculator)

(c) Find P(x > 65.2).

Zscore = (65.2 - 64) / 17

Zscore = 0.0705882

P(Z > 0.0705) = 0.4719 (Z probability calculator)