12.5
Circulation is the lifeblood of the publishing business. The larger the sales of a magazine, the more it can charge advertisers. Recently, a circulation gap has appeared between the publishers’ reports of magazines’ newsstand sales and subsequent audits by the Audit Bureau of Circulations. The data in the file represent the reported and audited newsstand yearly sales (in thousands) for the following 10 magazines:
Magazine Reported (X) Audited (Y) YM 621 299.6 CosmoGirl 359.7 207.7 Rosie 530 325 Playboy 492.1 336.3 Esquire 70.5 48.6 TeenPeople 567 400.3 More 125.5 91.2 Spin 50.6 39.1 Vogue 353.3 268.6 Elle 263.6 214.3
a. Construct a scatter plot. For these data, b0 = 26.724 and b1 = 0.5719.
b. Interpret the meaning of the slope, b1, in this problem.
c. Predict the audited newsstand sales for a magazine that reports newsstand sales of 400,000.
12.9
An agent for a residential real estate company in a large city would like to be able to predict the monthly rental cost for apartments, based on the size of the apartment, as defined by square footage. A sample of 25 apartments (stored in the file Rent) in a particular residential neighborhood was selected, and the information gathered revealed the following:
a. Construct a scatter plot.
b. Use the least-squares method to find the regression coefficients b0 and b1.
c. Interpret the meaning of b0 and b1 in this problem.
d. Predict the monthly rent for an apartment that has 1,000 square feet.
e. Why would it not be appropriate to use the model to predict the monthly rent for apartments that have 500 square feet?
f. Your friends Jim and Jennifer are considering signing a lease for an apartment in this residential neighborhood. They are trying to decide between two apartments, one with 1,000 square feet for a monthly rent of $1,275 and the other with 1,200 square feet for a monthly rent of $1,425. Based on (a) through (d), which apartment do you think is a better deal? Rent Size 950 850 1600 1450 1200 1085 1500 1232 950 718 1700 1485 1650 1136 935 72 6 875 700 1150 956 1400 1100 1650 1285 2300 1985 1800 1369 1400 1175 1450 1225 1100 1245 1700 1259 1200 1150 1150 896 1600 1361 1650 1040 1200 755 800 1000 1750 1200
12.17
In Problem 12.5 on page 417, you used reported magazine newsstand sales to predict audited sales (stored in the file Circulation). For that data, SSR = 130,301.41 and SST = 144,538.64. Magazine Reported Audited YM 621.0 299.6 CosmoGirl 359.7 207.7 Rosie 530.0 325.0 Playboy 492.1 336.3 Esquire 70.5 48.6 TeenPeople 567.0 400.3 More 125.5 91.2 Spin 50.6 39.1 Vogue 353.3 268.6 Elle 263.6 214.3
a. Determine the coefficient of determination, r2, and interpret its meaning.
b. Determine the standard error of the estimate.
c. How useful do you think this regression model is for predicting audited sales?