Project #4397 - Statistics - Inference

1.) Suppose 101 Randomly selected members of Myspace Karaoke were asked how much time they typically spend on the site during the week. The sample mean was found to be 4.2 hours. Assume that the population standard deviation is known to be s=2.5.

Cary Oakey computers the 95% confidence interval for the average time on the site and then states "95% of the members spend between 3.71 and 4.69 hours a week on the site" Is Carey correct?

 

Yes

No

 

2.) Every user of statistics should understand the distinction between statistical significance and practical importance. A sufficiently large sample will declare very small effects statistically significant. Consider the study of elite female Canadian athletes that investigated whether elite athletes are deficient in their nutritional intake. A total of n=201 athletes from eight canadian sports centers participated in the study. Female athletes were consuming an average of 2403.7 kcal/day with a standard deviation of 880 kcal/day. Suppose a nutritionist is brought in to implement a new health program for these athletes. This program should increase mean calorie intake but not change the standard deviation. Given the standard deviationn and how calorie deficient these athletes are, a change in the mean of 50 kcal/day to 2453.7 is of little importance. However, with a large enough sample, this change can be significant. To see this, calculate the P-value for the test of

 

H0:μ = 2403.7

Hα:μ > 2403.7

 

In the following situation:

 

A sample of 100 athletes, their average caloric intake is x = 2453.7

 

(round z to 2 decimal places and round p to 4 decimal places)

 

For n=100, z= ____ so P=P(Z>_____)=_____

 

3.) Hoping to attract more shoppers, a city builds a new public parking garage downtown. The city plans to  pay for the structure through parking fees. The consultant, who advised the city on the project, randomly seleced 44 weekdays. Daily fees collected averaged $126. Based on data from other parking structures, the consultant will assume parking fees at this parking garage are Normally distributed with a standard deviation of $15.

 

If a 95% confidence interval was constructed instead, how would the margin of effor compare to the one used to create the 90% confidence interval?

Subject Mathematics
Due By (Pacific Time) 04/14/2013 11:55 pm
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