Need help please

QUESTION 1

A class has 80 students. Test 2 had a class average of 78 and a variance of 49. Answer the following 7 questions by finding the closest matches). (Assume Normal distribution). Assume a 90-80-70-60 = A-B-C-D scale. 1. What is the probability of getting an A? 2. How many will get an A? 3. What is the probability of getting a B? 4. What is the probability of getting a C? 5. How many people will fail the class? 6. If the bottom 5% will get an F, what will be the cut-off score? 7. If the top 15% get an A, what is the cutoff score for an A?

QUESTION 2

A visit to a hospital emergency room for something as simple as a sore throat could have a mean cost of $322. Assume that this cost is normally distributed with a standard deviation of $83. If you want to be in the bottom 50%, what will be the cut-off dollar amount?

QUESTION 3

A visit to a hospital emergency room for something as simple as a sore throat could have a mean cost of $317. Assume that this cost is normally distributed with a standard deviation of $99. What is the cut-off dollar amount if you want to be in the top 3% of the patients?

QUESTION 4

For a standard normal distribution, the probability of obtaining a z value between -1.9 to 1.7 is

QUESTION 5

Pioneer company has given an aptitude test to 71 potential job applicants. The test score had an average of 81 and a standard deviation of 8. Aptitude tests are known to follow a t-distribution. Pioneer rejects the bottom 5% of the applicants right away. The top 5% are hired immediately at managerial positions. Answer the next 6 questions. a. What is the degrees of freedom for this distribution? b. What is the t-score for someone who has scored 93? c. What is the cutoff score for those who'll be hired as managers? d. What will be the cutoff score fro those who'll get rejected right away? e. If we want to define the middle of the class (80%) to be average, what will be the lower cut-off scores? f. If we want to define the middle of the class (80%) to be average, what will be the upper cut-off scores?

QUESTION 6

1. Suppose a tire manufacturer wants to set a mileage guarantee on its new XB 70 tire. Tests revealed that the tire's mileage is normally distributed with a mean of 47,900 miles and a standard deviation of 2,050 miles. The manufacturer wants to set the guaranteed mileage so that no more than 5 percent of the tires will have to be replaced. What guaranteed mileage should the manufacturer announce?

QUESTION 7

Suppose the probability of someone wearing a pair of glasses among 5th graders is 33.7%. If there are 44 kids in a class, what will be the standard deviation of this distribution?

QUESTION 8

Suppose the probability of someone wearing a pair of glasses among 5th graders is 21%. If there are 58 kids in a class, how many of them are expected to have glasses?