Miss Y, Spr 2020
STAT 10, Exam 3 Name:
| Question: | 1 | 2 | 3 | 4 | 5 | 6 | 7 | Total |
| Points: | 2 | 2 | 2 | 10 | 14 | 14 | 13 | 57 |
| Score: |
SHOW ALL WORK. Full credit will only be given if all correct work/steps are shown.
The following must be read and signed for the exam to be considered and counted in final grade.
I acknowledge that the following exam is entirely of my own work. Also, I acknowledge that
if Miss Y. finds my work suspicious of cheating, there may be consequences of failing this
exam or being reported to the Office of Student Conduct and Integrity.
Signature:
1. (2 points) What is the point estimate for the population mean, µ?
2. (2 points) What is the point estimate for the population proportion, p?
3. (2 points) The following graph shows the distribution of a sample that is not normal. What
could you change to make this distribution approximately normal?
4. (10 points) Complete parts a) and b).
a) Draw a normal curve with the following parameters µ = 168 and σ = 13. (Draw at least 2
standard deviations away from mean).
b) Find P(X ≥ 150).
5. (14 points) Alexa is a banshee in the wilderness of the kingdom of Ashlonian. Based on
recorded information, the mean decibel of Alexa’s shrieks is µ = 90 with a standard deviation
of σ = 17:8 decibels. Round all work to 3 decimal places.
a) Considering that we have a random sample of n = 50 shrieks, from the Central Limit
Theorem, what can you say about the ¯ x distribution?
b) What is µx¯?
c) Find the standard deviation of the sample mean, σx¯.
d) What is the probability that ¯ x is less than 95:6 decibels?
e) What is the probability that ¯ x is between than 84:3 and 89:2 decibels?
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6. (14 points) Becky, Jeffrey, and Huyen run several American BBQ and Korean BBQ fusion
restaurants. They serve tens of thousands of people yearly. A simple random survey of 1980
customers found that 297 gave negative reviews.
a) Obtain a point estimate for the population proportion of customers to one of the restaurants
that gave negative reviews. Also obtain ^ q.
b) Verify the three requirements for constructing a confidence interval about p are satisfied.
c) Construct a 95% confidence interval for the population proportion of customers who gave a
negative review. Round to 3 decimal places. (Find all notation for the critical value).
d) Interpret the interval.
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7. (13 points) A randomly chosen sample of 101 checks showed that the average number of times
Dale Gribble used his alias (Rusty Shackleford) to sign checks was ¯ x = 20:0 checks with a
standard deviation of s = 3:4 checks. We assume that Dale has written thousands of checks
over the years.
a) Verify the three requirements for constructing a confidence interval about µ are satisfied.
b) Say we want to make a 80% confidence interval, find tα=2 (be sure to find the notation of
α=2).
c) Make the 80% confidence interval.
d) Interpret the interval.
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