Wks 7, Chapter 6
____________, ____________: _______
Surname (e.g. “Straayer”), Given Name (e.g. “Dave”)
Class time
1. A population of values has a normal distribution with μ=100 and σ=15. You intend to draw a random
sample of size n=33.
What is the mean of the distribution of sample means? ____________________________
What is the standard deviation of sample means? ____________________________
Why or why not can we assume that shape of the distribution of sample means to be approximately
normal?
_________________________________________________________________________
2. Given data in problem 1, what is the probability that a single randomly-selected member of the
population is more than 120?
P(X>120) = _______________________________
3. Given data in problem 1, what is the probability that the average of a random sample of size 33 is
greater than 120?
P(X-bar>120) = _______________________________
4. Find the 90th percentile (P90). This is the value that separates the bottom 90% from the top 10% of
values.
5. Given samples of size 33, find the 90th percentile (P90) of the means.