7 of 8 ID: MST.CI.CIM.04.0010b [4 points] The Police Department is investigating

Question

7 of 8 ID: MST.CI.CIM.04.0010b [4 points] The Police Department is investigating the need for a speed camera to be implemented on Swift Road. A sample of 51 cars passing through that road on a particular day were randomly selected and their speeds recorded. The speed limit on Swift Road is 60 miles per hour (mph). The mean speed for the sample was calculated as 43 mph. The standard deviation of the speeds for the sample was calculated as 5 mph. The standard deviation for the population of cars driving on Swift Road is unknown. a) Select all the techniques that are commonly used to construct a confidence interval for the mean when the population standard deviation (a) is unknown Approximate the population standard deviation (o) with the sample standard deviation (s) O Replace the sample size (n) with n-1 Approximate the standard normal distribution with the Student's t distribution Decrease the confidence level to compensate for the increased margin of error b Calculate the upper and lower bounds of the 99% confidence interval for the mean speed traveled on Swift Road. Give your answers in mph to 2 dec Upper bound = Lower bound a pace. mph mph 8 of 8 ID: MST.HT.TM.05.0020 [1 point Rick the receptionist claims that he types an average of 70 words per minute. In order to test this, Rick's boss gives him 15 different one minute typing challenges throughout the day. On each challenge, Rick's boss records the number of words typed. The boss calculates the sample mean to be 67 words per minute and the sample standard deviation to be 16 words per minute. He calculates a test statistic for the following hypothesis test: Ho: ?-70 Assuming the null hypothesis is true, this test statistic will follow: the standard normal distribution the t distribution with 16 degrees of freedom the t distribution with 15 degrees of freedom the t distribution with 14 degrees of freedom

Explanation / Answer

8)

Given n= 15

Df = n-1 = 14

Since sample size is less than 30 we use t distribution.

T distribution with 14 degrees of freedom

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