math 9 & 10
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ShortExercise9.docxBUSA 2183 Introduction to Business Statistics
Summer 2019 –Session II
Short Exercise 9 (25 points)
IMPORTANT: In any question, if there is a calculation, first provide the formula and then show your calculations for your answers.
Please, provide your answers under each question.
Data files can be found in the D2L.
Question 1 (Short Exercise 2 in the book) (5 points)
A sample of 81 observations is taken from a normal population with a standard deviation of 5. The sample mean is 40. Determine the 95% confidence interval for the population mean.
Question 2 (Short Exercise 3 in the book) (4*2=8 points)
A sample of 250 observations is selected from a normal population with a population standard deviation of 25. The sample mean is 20.
a.Determine the standard error of the mean.
b.Determine the 95% confidence interval for the population mean.
Question 3 (Short Exercise 10 in the book) (2*2=4 points)
Use Appendix B.5 to locate the value of t under the following conditions.
a.The sample size is 15 and the level of confidence is 95%.
b.The sample size is 24 and the level of confidence is 98%.
Question 4 (Short Exercise 15 in the book) (3+3+2=8 points)
The owner of the West End Kwick Fill Gas Station wishes to determine the proportion of customers who pay at the pump using a credit card or debit card. He surveys 100 customers and finds that 80 paid at the pump.
a.Estimate the value of the population proportion.
b.Develop a 95% confidence interval for the population proportion.
c.Interpret your findings.
