Aj Davis Department Stores

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AJ Davis Department Stores - Project Part A, B, and C
Stacie Borowicz
June 14, 2013
Math 533

Project Part A – Exploratory Data Analysis
Credit Balance ($)

Based on a sample of 50 customers, the credit balance for customers of Davis Department stores is on average $3970.00. Based on the graph, 18 of the 50 sampled fall below and 17 fell above the average. The standard deviation for credit balance is 931.9.

Income

Annual Income of Davis Department Stores customers range anywhere from $22,000 to $67,000. Majority of their customers have an annual income of about $43,740. The standard deviation for income is $14,640.

Size

Average household size is about 3.4. Based on the graph above, 15 of the 50 sampled have a
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10. For a household size of 10 the confidence interval is (5926.96, 7320.36) which will include the mean credit balance and the prediction interval is (5195.30, 8052.01) which will include the actual credit balance for a household of that size.
11.
Regression Equation

Credit Balance($) = 1276.02 + 32.2719 Income ($1000) + 346.852 Size + 7.88209 Years

(Appendix C)

APPENDIX A
General Regression Analysis: Credit Balance($) versus Size

Regression Equation

Credit Balance($) = 2591.44 + 403.221 Size

Coefficients

Term Coef SE Coef T P
Constant 2591.44 195.064 13.2851 0.000
Size 403.22 50.946 7.9147 0.000

Summary of Model

S = 620.162 R-Sq = 56.62% R-Sq(adj) = 55.71%
PRESS = 19992921 R-Sq(pred) = 53.02%

Analysis of Variance

Source DF Seq SS Adj SS Adj MS F P
Regression 1 24092210 24092210 24092210 62.6421 0.000000 Size 1 24092210 24092210 24092210 62.6421 0.000000
Error 48 18460853 18460853 384601 Lack-of-Fit 5 2499467 2499467 499893 1.3467 0.263274 Pure Error 43 15961386 15961386 371195
Total 49 42553062

Fits and Diagnostics for Unusual Observations

Credit
Obs Balance($) Fit SE Fit Residual St Resid 5 1864 3397.89 113.691 -1533.89 -2.51600 R

R denotes an observation with a large standardized residual.

APPENDIX B

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