Question

A population of values has a normal distribution with μ= 106.9 and σ=14.5
You intend to draw a random sample of size n=20

What is the probability that a single randomly selected value is less than 109.8?
P(X < 109.8)
How do you the probability that a sample of size n= 20 is randomly selected with a mean less than 109.8?
P(M < 109.8)

Also, I have to round the answer to the 4th decimal place. How do I do that?

Answer 1

Step-by-step explanation:

Find the z-score.

z = (x − μ) / σ

z = (109.8 − 106.9) / 14.5

z = 0.2

Use a chart or calculator to find the probability.

P(Z < 0.2) = 0.5793

Find the mean and standard deviation of the sampling distribution.

μ = 106.9

σ = 14.5 / √20 = 3.242

Find the z-score.

z = (x − μ) / σ

z = (109.8 − 106.9) / 3.242

z = 0.894

Use a calculator to find the probability.

P(Z < 0.894) = 0.8145