STAT 200 Quiz 2

Use Table (http://www.itl.nist.gov/div898/handbook/eda/section3/eda3671.htm) to find the proportion of the normal curve that is

1)    Between a z-score of .60 and the mean

2)    Between a z-score of 1.60 and the mean

3)    At or above a z-score of 1.30

4)    At or below a z-score of 1.30

5)    At or below a z-score of -1.00

6)    At or above a z-score of -1.00

7)    Between the z-scores of -1.00 and .60

8)    Between the z-scores of -1.50 and .65

9)    Between the z-scores of -1.96 and .25

Part II

1.   What percentage of a normal distribution is within 2 standard deviations of the mean? (Select the closest answer)

The lengths of time bank customers must wait for a teller are normally distributed, with a mean of 3 minutes and a standard deviation of 1 minute.

2.  What proportion of bank customers waits between 2 and 3.5 minutes

•a.  What percentage wait more than 4 minutes?

•b.  What proportion waits between 1 and 2.5 minutes?

•c.  What percentage wait less than 1 minute?

3.  To estimate the medical charges for an appendectomy Blue Star Insurance has data from a random sample of 70 patients. The sample mean cost is $510, with a sample standard deviation of $70

Construct a 95% confidence interval for the population mean cost.

4.  We are 95% confident that the populations mean costs of patients’ medical charges for an appendectomy through Blue Star Insurance range is between _____________ and ________________.

A real estate agent records the ages of 50 randomly selected home buyers in her sales area. The mean age is 38 years, with a sample standard deviation of 10 years.

Find a 99% confidence interval for the mean age.