Download Prof. Fischthal MATH 114 Chapters 9 and 10 REVIEW

Prof. Fischthal
MATH 114
Chapters 9 and 10
REVIEW
You may use a calculator BUT you must show all formulas and steps used to get full credit!! No matter how easy a problem might be, you
must show all steps used when coming up with a solution. The answer “I did it in my head” or “I worked it out logically” will not be
accepted unless you explain what you did.
In any question where you are using the normal distribution you must show an appropriate graph.
1. To test the noise level of a certain model dishwasher a random sample of 49 items is selected and found to have
an average noise level of 49.5 dB with a sample standard deviation of 2.8 dB. Use hypothesis testing notation for
parts c and d.
a. What is the point estimate of the mean noise level of the population consisting of all the dishwashers of this
model?
b. What is a 96% confidence interval of the mean noise level of this population?
c. The manufacturer claims the mean noise level is 48. 8. At the 96% level is there reason to question the
manufacturer’s claim? Explain.
d. At the 96% level is their reason to say the manufacturer’s claim in part c above is too low? Explain.
2. Two different factories, A and B, produce the same item. To see whether one factory has better quality control
samples are tested from both. Plant A had 100 items tested found an average of 2.9 defects with a sample standard
deviation of .4. Plant B had 72 items tested and found and average of 2.7 defects with a sample standard deviation
of .6. Using hypothesis testing notation, at a 99% level can we say there is no difference in the quality of the items
from each plant?
3. To test whether the manufacturing process for dice produces a “fair” die a die is tossed 150 times and found that a
six comes up 30 times. Using hypothesis testing notation at a 95% level can we say
a. that the die is fair?
b. that the die favors six coming up more frequently that expected?
c. using the sample data what is the point estimate of P(six)?
4. Nabisco claims that the mean number of chocolate chips in their cookies in 15. A sample of 16 cookies is checked
and found that the average was 14 with a standard deviation 2. Using hypothesis testing notation, at a 90% level
can we say
a. their claim is accurate?
b. Can we say it’s too high?