stat help

Simple Regression Study Guide

Not Assigned…Use as a guide for preparing for final exam

Store ID	Shelf Space Allocated to Pet Food =X	Weekly Pet Food Sales in Hundreds of Dollars =Y
1	5	1.6
2	5	2.2
3	5	1.4
4	10	1.9
5	10	2.4
6	10	2.6
7	15	2.3
8	15	2.7
9	15	2.8
10	20	2.6
11	20	2.9
12	20	3.1
13	25	3.3
14	25	3.5
15	25	3.4

Review the example study provided in this handout to become familiar with Minitab commands and statistical testing needed to complete the Aslin Finch pet food problem.

Research Objective: The marketing manager of Aslin Finch would like to determine the effect of shelf space on the weekly sales of pet food. A random sample of 15 stores is selected with the following results. Set alpha at .01.

Practice by entering the data into Minitab and analyzing the model. When you can address each of the “Label” items for multiple regression you are ready to take the final. Simple regression is used to build your confidence and because the data is limited and therefore easier to study. The final exam is largely based on multiple regression but some of the calculations are required. These calculations will be identified during lecture.

1-Label: Problem Definition (why are you doing this analysis?)

Begin with Problem Definition

2-Label: Scatterplot

Use Minitab Scatterplot with description of relationship between x and y. Describe scatterplot to determine whether positive or negative and explain how you made this determination in your graph description? Neither?

3-Label: Correlation Coefficient

Hypothesis test of correlation coefficient to determine if a linear relationship exists between Feet of Shelf Space and Weekly Pet Food Sales– Use six step process

4-Label: Regression Equation (show only the equation not the entire table or output)

Use Minitab to develop the regression equation-In your report, paste the Minitab output of regression equation and define regression coefficients b0 and b1 as learned during lecture.

bo = and is defined as…

b1= and is defined as….

Be sure to include the quantitative assessment of each in terms of pet food sales.

5-Label: Significance Testing (Regression Coefficient) Is x a significant predictor of y?

T test for significance of regression coefficient Use six step process in interpretation step discuss average amount of change in y for one unit change in x.

6-Label: Significance Testing (ANOVA) What percentage of error or variation is …

F Test to test R-sqd – Use six step process and in interpretation step discusses percentage of variability in y explained by x. Use six step process

7-Label: Satisfying Regression Assumptions (Normality and constant variance)

Minitab plots to include in report: Size graphs to fit neatly within report and place each description with the graph you are discussing.

NP Plot for residuals -Minitab graph with description addressing to assumption(s)

Residuals vs. Fits-Minitab graph with description addressing to assumption(s)

Residuals and x variable-Minitab graph with description addressing to assumption(s)

Graphical analyses must describe residuals plotted on graphs. Each graph must speak to the assumption and how the graphed residuals support or violate the assumption.

8-Label: Confidence Interval for Regression Coefficient

Develop confidence interval for regression coefficient and interpret –Calculations to be done by hand and typed neatly onto report. Discuss whether 0 lies in interval and interpret interval in terms of pet food sales and shelf space.

9-Label: Prediction and Confidence Interval for Fit value of Y

Use Minitab to develop prediction interval and confidence interval for y for a value of x you select and enter into Minitab – Interpret both intervals as they relate to y