Vol. 9, No. 4

April 2007

PQ Systems
 
Contents

Tidying up the control chart

Quality Quiz: With a video!

MSA with Jackie Graham

Data in everyday life

Bytes and pieces

FYI: Current releases

 

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Software

 

   

Quality Quiz:

Click here for a more complete video explanation

The division manager, Emily Dickinson, has decided that Hyde N. Sikh has not lived up to her expectations, so she releases him from his responsibilities. While quality manager Polly Yurathane had actually been responsible for miscalculations made by Hyde N. Sikh, she was unscathed, and moved eagerly to work with her new boss, Hy O. Pinyon, a statistician who, she believes, will help her to learn more about statistics.

Hy comes across a regression model prepared by Polly earlier in the year, and asks her to explain the results:

= cost

= amount of coal mined

depth of shaft

Month

Total cost

Tons of coal

Depth of shaft

JAN

5

10

5

FEB

9

20

5

MAR

13

30

5

APRIL

14

10

20

MAY

18

20

20

JUNE

22

30

20

JULY

20

10

30

AUG

24

20

30

SEPT

28

30

30

Regression for cost:

Variable

Coefficient

Standard error

Beta coefficient

t-value

p-value

Constant

2

1.067

0

 

<0.001

Tons mined

0.4

1.581

1

3.162

0.007

Shaft size

0.6

1.005

3

5.969

<0.001

 

 

 

 

 

 

R-squared

0.7526

 

 

 

 

R-squared (adj)

0.7196

 

 

 

 

As he examines the data, Hy refers to the regression coefficient of and . Polly, eager to convince him of her statistical prowess, explains their meaning, noting that the printout also includes beta coefficients, which represent standardized values.

Is Polly’s assessment of this meaning accurate?

a) Yes.

b) No.

 

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