Question

we choose a sample of size 100 from a population of monthly cable bills having standard deviation $20 If we assume the population mean bill is $65, what is the probability mean of our sample is greater than $70.

Answer 1

0.0062

Explanation:

Find the standard error.

σ = 20 / √100

σ = 2

Find the z-score.

z = (x − μ) / σ

z = (70 − 65) / 2

z = 2.5

Find the probability.

P(Z > 2.5) = 1 − 0.9938

P(Z > 2.5) = 0.0062