In: Math
Use the data given in the table to answer the following questions. The data represents the average number of miles that a salesperson travels in a day verses the number of sales made each month.
Miles, x | 24 | 32 | 75 | 41 | 76 | 107 | 32 | 46 | 112 |
Sales, y | 76 | 58 | 190 | 112 | 141 | 235 | 24 | 147 | 188 |
(a) What is the value of the correlation coefficient for this set of data? Round to 3 decimal places.
(b) What is the equation of the Regression Line for this set of
data? Round values to two decimal places.
(c) Predict the number of sales an associate could expect to make
if he travelled an average of 108 miles each day. Round to two
decimal places.
a)
x | y | (x-x̅)² | (y-ȳ)² | (x-x̅)(y-ȳ) |
24 | 76 | 1336.31 | 2928.01 | 1978.06 |
32 | 58 | 815.42 | 5200.01 | 2059.17 |
75 | 190 | 208.64 | 3586.68 | 865.06 |
41 | 112 | 382.42 | 328.01 | 354.17 |
76 | 141 | 238.53 | 118.57 | 168.17 |
107 | 235 | 2157.09 | 11001.68 | 4871.51 |
32 | 24 | 815.42 | 11259.57 | 3030.06 |
46 | 147 | 211.86 | 285.23 | -245.83 |
112 | 188 | 2646.53 | 3351.12 | 2978.06 |
ΣX | ΣY | Σ(x-x̅)² | Σ(y-ȳ)² | Σ(x-x̅)(y-ȳ) | |
total sum | 545 | 1171 | 8812.222222 | 38058.9 | 16058.44 |
mean | 60.56 | 130.11 | SSxx | SSyy | SSxy |
correlation coefficient , r = Sxy/√(Sx.Sy) = 0.877
b)
sample size , n = 9
here, x̅ = Σx / n= 60.56 ,
ȳ = Σy/n = 130.11
SSxx = Σ(x-x̅)² = 8812.2222
SSxy= Σ(x-x̅)(y-ȳ) = 16058.4
estimated slope , ß1 = SSxy/SSxx = 16058.4
/ 8812.222 = 1.8223
intercept, ß0 = y̅-ß1* x̄ =
19.7612
so, regression line is Ŷ = 19.76
+ 1.82 *x
c)
Predicted Y at X= 108 is
Ŷ = 19.76119 +
1.822292 * 108
= 216.57