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ECON2300

Homework 7

1. Kevin Horn is the national sales manager for National Textbooks Inc. He has a sales staff of 40 who visit college professors all over the United States. Each Saturday morning, he requires his sales staff to send him a report. This report includes, among other things, the number of professors visited during the previous week. Listed below, ordered from smallest to largest, are the number of visits last week.

a. Determine the median number of calls.

b. Determine the first and third quartiles.

c. Determine the first decile and the ninth decile.

d. Determine the 33rd percentile.

2. The following graph is an ogive of the mathematics scores on the SAT. The vertical axis in an ogive is the cumulative relative frequency and can also be interpreted as a percentile.

(a) Find and interpret the percentile rank of a student who scored 450 on the SAT mathematics exam.

(b) Find and interpret the percentile rank of a student who scored 750 on the SAT mathematics exam.

(c) If Jane scored at the 44th percentile, what was her score?

3. (MGH CH4 Exercise 10) The box plot shows the undergraduate in-state tuition per credit hour at four year public colleges.

a. Estimate the median.

b. Estimate the first and third quartiles.

c. Determine the interquartile range.

d. Beyond what point is a value considered an outlier?

e. Identify any outliers and estimate their values.

f. Is the distribution symmetrical or positively or negatively skewed?

4. A credit card company has a fraud detection service that determines ifa card has any unusual activity. The company maintains a database of daily charges on a customer’s credit card. Days when the card was inactive are excluded from the database. Ifa day’s worth of charges appears unusual, the customer is contacted to make sure that the credit card has not been compromised. Use the following daily charges (rounded to the nearest dollar) to determine the amount the daily charges must exceed before the customer is contacted.

5. (MGH CH4 Exercise 14) Listed below are the salaries, in $000, for a sample of 15 chief financial officers in the electronics industry.

a. Determine the mean, median, and the standard deviation.

b. Determine the direction of skewness using Pearson’s method or the software method.