Question

A sales manager for an advertising agency believes there is a relationship between the number of contacts that a salesperson makes and the amount of sales dollars earned.

A regression analysis shows the following results:

	Coefficients	Standard Error	t Stat	p value
Intercept	−12.201	6.560	−1.860	0.100
Number of contacts	2.195	0.176	12.505	0.000

ANOVA
	df	SS	MS	F	Significance F
Regression	1.00	13555.42	13555.42	156.38	0.00
Residual	8.00	693.48	86.68
Total	9.00	14248.90

Additional information needed to perform the calculation x⎯⎯=33.4, ∑(x−x⎯⎯)2=2,814.4.x¯=33.4, ∑(x-x¯)2=2,814.4. Calculate a 95% confidence interval for the situation where x = 30 calls. (Round your final answers to one decimal).

Multiple Choice

• 46.7 and 60.6

• 31.1 and 76.2

• 51.4 and 55.9

• 55.8 and 51.5

Answer 1

n=	10
bo=	-12.201
b1=	2.1950
sxy =√MSE=	9.3102
Sxx=(n-1)sx^2=	2814.4
x̅ =	33.4

predcited value at X=30:		53.6490
std error confidence interval=		s*√(1/n+(x0-x̅)2/Sxx)		=	3.0040
for 95 % CI value of t=					2.3060
margin of error E=t*std error                            =					6.9272
lower confidence bound=sample mean-margin of error =					46.7
Upper confidence bound=sample mean+margin of error=					60.6

correct option is : 46.7 and 60.6