STAT 200 Final Exam (spring 2017) STAT 200 Final Exam | Page 6

( b) What is the probability that 36 randomly selected test scores will have a mean test score that is between 148 and 152?
13. ​An insurance company checks police records on 500 randomly selected auto accidents and notes that teenagers were at the wheel in 80 of them. Construct a 95 % confidence interval estimate of the proportion of auto accidents that involve teenage drivers. ​Show all work. Just the answer, without supporting work, will receive no credit.
14. ​A city built a new parking garage in a business district. For a random sample of 60 days, daily fees collected averaged $ 2,000, with a standard deviation of $ 400. Construct a 95 % confidence interval estimate of the mean daily income this parking garage generates. ​Show all work. Just the answer, without supporting work, will receive no credit.
15. ​ABC Company claims that the proportion of its employees investing in individual investment accounts is higher than national proportion of 45 %. A survey of 200 employees in ABC Company indicated that 100 of them have invested in an individual investment account.
Assume we want to use a 0.10 significance level to test the claim.
( a) Identify the null hypothesis and the alternative hypothesis.
( b) Determine the test statistic. ​Show all work; writing the correct test statistic, without supporting work, will receive no credit.
( c) Determine the ​P​-value for this test. ​Show all work; writing the correct P-value, without supporting work, will receive no credit.
( d) Is there sufficient evidence to support ABC Company’ s claim that the proportion of its employees investing in individual investment accounts is higher than 45 %? Explain
16. Mimi was curious if regular excise really helps weight loss, hence she decided to perform a hypothesis test. A random sample of 5 UMUC students was chosen. The students took a