## Answered: - ECO250 Statistics Tutors please: I need help with these ex

I need help with these examples, but kindly ask also for the formulas, or "key" words that I seem to have an issue with. I truly want to understand how I get the? answers.

thank you.

Practice Q2

Question 1

The time required to verify and fill a common prescription at a neighborhood pharmacy is normally distributed with a

mean of 10 minutes and a standard deviation of 3 minutes.

What is the probability that a customer will have to wait more than 15 minutes for her prescription to be verified and

filled?

Write your answer as a probability (i.e., a number between 0 and 1).

Question 2

The time required to verify and fill a common prescription at a neighborhood pharmacy is normally distributed with a

mean of 10 minutes and a standard deviation of 3 minutes.

What is the probability that a customer will have to wait less than 8 minutes for her prescription to be verified and filled?

Write your answer as a probability (i.e., a number between 0 and 1).

Question 3

The time required to verify and fill a common prescription at a neighborhood pharmacy is normally distributed with a

mean of 10 minutes and a standard deviation of 3 minutes.

Determine the wait time for which 80% of all prescriptions will be verified and filled.

Question 4

The credit score of a 35 year old applying for a mortgage at Ulysses Mortgage Associates is normally distributed with a

mean of 600 and a standard deviation of 100. Determine the interval of credit scores around the mean that includes

approximately 68% of credit scores.

Lower bound: .

Upper bound:

.

Question 5

The credit score of a 35 year old applying for a mortgage at Ulysses Mortgage Associates is normally distributed with a

mean of 600 and a standard deviation of 100. Determine the interval of credit scores around the mean that includes

approximately 95% of credit scores.

Lower bound: .

Upper bound: .

Question 6

Jim's systolic blood pressure is normally distributed random variable with a mean of 145 mmHg and a standard deviation

of 20 mmHg. If Jim's systolic blood pressure is taken at a randomly chosen moment, what is the probability that it will be

between 125 and 165?

Write your answer as a probability (i.e., a number between 0 and 1).

Question 7

Chlorine concentration in a municipal water supply is a uniformly distributed random variable that ranges between 0.74

ppm and 0.98 ppm.

Calculate the mean chlorine concentration.

Question 8

Chlorine concentration in a municipal water supply is a uniformly distributed random variable that ranges between 0.74

ppm and 0.98 ppm.

Calculate the standard deviation.

Question 9

Chlorine concentration in a municipal water supply is a uniformly distributed random variable that ranges between 0.74

ppm and 0.98 ppm.

Calculate the probability that the chlorine concentration will exceed 0.80 ppm.

Write your answer as a probability (i.e., a number between 0 and 1).

Question 10

Chlorine concentration in a municipal water supply is a uniformly distributed random variable that ranges between 0.74

ppm and 0.98 ppm.

Calculate the probability that the chlorine concentration will be between 0.80 ppm and 0.90 ppm.

Write your answer as a probability (i.e., a number between 0 and 1).

Question 11

Suppose the average weight for population of men is 178 pounds. You draw a random sample of 10 men and record the

following weights:

150, 145, 180, 200, 175, 190, 142, 175, 240, 150.

Calculate the sampling error.

Question 12

Generation Y has been defined as those individuals who were born between 1981 and 1991. According to the Project on

Student Debt, Generation Y students graduating from college average \$23,200 in debt. Assume the standard deviation

for debt is \$7,500 per student.

What is the probability that the sample mean will be less than \$24,000 for a sample of 30 students?

Write your answer as a probability (i.e., a number between 0 and 1).

Question 13

A teacher needs to grade 200 exams. She claims that exams require an average of 12 minutes to grade with a standard

deviation of 3 minutes. A random sample of 36 exams is selected.

Suppose the sample mean is 11 minutes. What is the probability that the sample mean will be less than or equal to 11

minutes if the actual sampling distribution mean equals 12 minutes?

Question 14

A teacher needs to grade 200 exams. She claims that exams require an average of 12 minutes to grade with a standard

deviation of 3 minutes. A random sample of 36 exams is selected.

Suppose the sample mean is 11 minutes. Is the teacher's claim valid?

No Yes

Question 15

A teacher needs to grade 200 exams. She claims that exams require an average of 12 minutes to grade with a standard

deviation of 3 minutes. A random sample of 36 exams is selected.

Identify the symmetrical interval that includes 95% of the sample means if the true population mean is 12 minutes.

Lower bound:

minutes.

Upper bound:

minutes.

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