1. The quick sell dealership started an ad campaign. During a 10 week campaign the dealer kept the following records:
# of adds per week (x)
6
20
0
14
25
16
28
18
10
8
# of cars sold per week (y)
15
31
10
T
28
20
40
25
12
15
(i) Given the covariance is 76.5 and the S(y) = 9.58, calculate the product moment correlation (r), correct to two decimal places.
Using the equation r = Sxy/SxSy it will solve as follows: r = 76.5 / 9.58(8.7).
Significant figures answer is .92
(ii) Use your result to comment on the statement : The more ads posted, the more cars sold.
The result from (i) [.92] indicates that there is a strong relationship between number of ads and number of car sales.
(iii) Given that the mean of y is 21.20, find the equation of the line of y on X.
Using (y-ymean) = Sxy/Sx(x-xmean) the solution is (y-21.20)= 76.5/8.7(x-14.5)
Simplified, this will be y= 8.79x-106.25
Using the least squares regression line to predict the following:
(iv) Calculate the # of cards sold if 14 ads per week were published.
Use the equation found in the above portion to predict the number of cars that would be sold(y), if 14 ads were published(x)
y= 8.79(14)-106.25
y=16.81
