STATS 240 Exam 2 Spring 2021
NAME_________________________________________________________________________________________
SUFFOLK UNIVERSITY
STATS 240 – Section __
SPRING 2021
EXAM 2
General instructions:
1. Box final answers.
2. Neatly show details of work for full credit and to allow the possibility of partial credit.
3. Calculators are allowed on this exam. You may not share calculators. You may not
communicate with people other than your professor during this exam.
1. [10pts] The number of chocolate chips in a bag of Chips Ahoy! Chocolate chip
cookies are approximately normally distributed, with a mean of 1262 chips and a
standard deviation of 118 chips. Find the number of chocolate chips that make the
90th percentile of the number of chocolate chips in the bag.
Note: Choose ONE problem from #2 and #3. You don’t have to do both problems.
2. [10pts] Despite its nutritional value, seafood is only a tiny part of the American diet,
with the average American eating just 16 pounds of seafood
per year with a
standard deviation of 3.2 pounds. Janice takes a random sample of 42 Americans.
Find the probability that the sample mean seafood consumption of the 42
Americans is more than 17.5 pounds Use 4 non-zero decimal places in your
calculations. Round z-values to 2 decimal places.
3. [10pts] According to a study done by Wakefield Research, the proportion of
Americans who can order a meal in a foreign language is 47%. Suppose a random
sample of 200 Americans is taken, find the probability that the sample proportion
of Americans who can order a meal in a foreign language is less than 55% Use 4
non-zero decimal places in your calculations. Round z-values to 2 decimal places.
4. [20pts] A random sample of 30 Suffolk University employees had an average
commute length of 11.7 miles, with a standard deviation of 8.5 miles. What is the
90% confidence interval for the mean commute length of all Suffolk employees
Use 4 non-zero decimal places in your calculations.
(a) Find the α
2 ,
(b) Find σ