# Homework 2

Exercises 6.1

1. Use the Hospital charges worksheet in the file Chpt 4-1.xls

a. Calculate the mean and the median for Age, LOS, and Charges by using the =AVERAGE( ) and =MEDIAN( ) functions.

b. Based on these, in what direction are these distributions skewed, if at all?

c. Calculate the variance and standard deviation of Age, LOS, and Charges by using the formulas in Equations 6.3 and 6.4.

d. Calculate the variance and standard deviation of Age, LOS, and Charges by using the =VAR( ) and =STDEV( ) functions. Make sure that the results in (c) match those in (d).

Exercises 6.2

1. Use the Hospital charges worksheet in the file Chpt 4-1.xls.

a. Based on the mean and standard deviation for LOS, generate a frequency distribution in terms of one standard deviation units around the mean.

b. Develop the Excel chart to show the frequency distribution generated in (a).

8. Assume a mean of 75 mmhg and standard deviation of 5 mmhg is for diastolic blood pressure. Use the =NORMDIST( ) function to determine the following:

a. The proportion of people who have diastolic blood pressure less than 76 mmhg

c. The proportion of people who have diastolic blood pressure greater than 73 mmhg

Exercises 6.4

4. A hospital knows that 0.646 of the persons coming to emergency room come for true emergencies. Using the formulas in this section and the binomial distribution, calculate the mean and standard deviation for any ten arrivals at the emergency room.

Exercises 6.5

1. Use the formula in Equation 6.15 to determine the following standard errors:

a. p = 0.3, n = 80

b. p = 0.5, n = 80

c. p = 0.3, n = 250

d. p = 0.5, n = 250

2. A practice of eighteen dentists upgraded their computer system and suspects that in the process they lost information on recalls for many of their patients. They drew a simple random sample of two hundred patient records and discovered that twenty-two of those had follow-up calls that were not included in the new computer system. Use the =NORMDIST( ) function to determine the following:

a. The probability that the true proportion of missed follow-up calls is less than 10 percent among all records

b. The probability that the true proportion of missed follow-up calls is greater than 20 percent among all records

Exercises 6.6

1. What is the number of degrees of freedom in each of the following?

a. A sample of ten observations

b. A sample of one hundred observations

c. A sample of two hundred and fifty observations

2. What is the two-tail probability in each of the following?

a. n = 10, S.E. from the mean = 2

b. n = 10, S.E. from the mean = 3

c. n = 100, S.E. from the mean = 2

3. What is the one-tail probability in each of the following?

a. n S.E.

b. n S.E.

c. n S.E.

4. How many standard errors from the mean are the following assuming two-tail results?

a. p = 0.05, n = 10

b. p = 0.12 n = 10

5. How many standard errors from the mean are the following assuming one-tail results?

a. p = 0.05, n = 10

b. p = 0.12 n = 10