In: Statistics and Probability
In 2013, the average length of a feature length film was 86
minutes
with a standard deviation of 24 minutes. Source:
IMDB.com/interfaces
a) Explain why it is inappropriate to use the normal model to find
the probability
that a random sample of 15 films will have a mean length greater
than 115
minutes.
b) Describe the sampling distribution of x for n = 40 films (Shape,
Center,
Spread, with justification).
c) Using the Standard Normal Table, find the proportion of samples
of size
n = 40 that will have a mean length greater than 115 minutes.
d) Will the proportion found in c) be greater than or less than the
proportion of
samples of size n = 65 that will have a mean length greater than
115 min?
Explain.
e) There is a 4% probability that a random sample of 40 films will
have a mean
length greater than ______. (Use the Standard Normal Table.)