13.28Homework

NCSS

Based on the scatter plot and residual plot of errors/residuals versus X (feet or size), the regression assumptions do not appear to be violated.

The SLR model is useful. With at least 95% confidence (really using the pvalue with almost 100% confidence), we conclude square feet is significantly related to hours needed to move.

Manual/Excel

14.45Homework

NCSS

city suburban

From NCSSDescriptive Statistics

Holding constant the effect of location, for each point increase in summated rating, estimated cost of a meal increases by $1.27.For a given summated rating, the estimated mean cost of a meal in a suburban restaurant is $4.37 less (than the base, the estimated mean meal cost in a city restaurant.

€

When X1 = 0, location is city. Thus,

ˆ Y = −30.5969 +1.2704X2

For restaurants in the city location, for a 1 unit increase in summated rating, estimated meal cost increases by $1.27.

€

When X1 =1, location is suburban. Thus,

ˆ Y = −30.5969 − 4.3711(1) +1.2704X2

ˆ Y = −34.968 +1.2074X2

For restaurants in the suburban location, for a 1 unit increase in summated rating, estimated meal cost increases by $1.27.

14.46Homework

NCSS

Newspaper$Low, 25

Newspaper$High, 55

Radio$Low, 25 770 1935Radio$High, 65 1598 1662

€

X2 = 25 Radio$Low

ˆ Y = -201.8 + 38.855X1

€

ˆ Y = −1293.31+ 56.93X1 + 43.66X2 − 0.843X1X2

where X1 = Newpaper$ and X2 = Radio$

X2 Radio$Low=25

€

X2 = 65 Radio$High

ˆ Y =1544.6 +2.135X1

X2 Radio$High=65

There is evidence of a significant interaction effect. For high levels of Radio Advertising spending, whether we spend a small amount or large amount on newspaper advertising doesn’t really matter in terms of sales.Just the opposite is true for low levels of Radio Advertising spending. If we spend a high amount on newspaper advertising, in this case, we do see major gains in sales.

We cannot say, more spending on newspaper advertising is associated with higher sales.We cannot say, more spending on radio advertising is associated with higher sales. This is because the interaction is significant, and the effect we get from spending more in newspaper advertising depends on our level of radio advertising spending, and vice-versa.

Explaining the significant interaction

Assumptions Check

We are okay!

Assumptions Check - Multicollinearity

Almost no multicollinearity at all!

15.7Homework

15.7Homework

NCSS

Maybe an assumption violation, i.e. independent errors