( a ) Consider all random samples of 36 test scores . What is the standard deviation of the sample means ?
( 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 .