Question

The distribution of textbook sales for all college students is right (Rt.) skewed with a mean of $300 and a standard deviation of $120. Suppose that a researcher who didn’t know this information sampled 40 students. She found that the students paid $280 on average with a standard deviation equal to $109. What is the sampling distribution of the sample mean for a sample of size 40?

a) Shape: Approx. Normal Mean: 300   Stdev: 120

b) Shape: Approx. Normal Mean: 280   Stdev: 109

c) Shape: Approx. Normal Mean: 300   Stdev: 120/ √40

d) Shape: Approx. Normal Mean: 300   Stdev: 109/ √40

Answer 1

Solution:

We are given

µ = 300

σ = 120

n = 40

Mean for sampling distribution of sample means = µ = 300

Standard deviation of sampling distribution of sample means = σ/sqrt(n) = 120/sqrt(40) = 18.97367

Answer:

c) Shape: Approx. Normal Mean: 300   Stdev: 120/ √40