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Sue0113

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The following table gives the sales experience (in Months) and the number of computers sold during the previous month by 7 sales persons
Experience 4,12,9,6,10,30,7
Sales 19,42,28,31,39,30,21

using minitab output write the straight line (least squares) equation and the coefficient
The regression equation is Sales = 27.2 + 0.252 exp

Predictor Coef SE Coef T P
Constant 27.195 5.781 4.70 0.005
Exp 0.2517 0.4201 0.60 0.575

s=8.97833 R-Sq=6.7%

so this is where I am
4,6,7,9,19,12,30 I know the yis 27.195 and slope is 0.252
19,21,28,30,31,39,42

X Y Product
4-9=-5 19-30=-11 55
6-9=-3 21-30=-9 27
7-9=-2 28-30=-2 4
9-9=0 30-30=0 0
10-9=1 31-30 =1 1
12-9=3 39-30=9 27
30-9=21 42-30=12 252

55+27+4+0+1+27+252=366

(n-1)*sx*sy =correlation coeficient

correlation = 0.82385 So now how do I get the straight line equation? y=mx+b so 27.195=(.25175) (????)+27.19512
c)The I need to calculate 2 points to draw line on graph and give calculations.
d)Interpet what the slope means in term of the problem.
e)Identify a possible outlier, remove it and recalculate the new least squares line.
f)using my equation from (e)predict the number of sales for a person with 15 months experience.
g)can this model determine sales targets.
 
Sue0113 said:
The following table gives the sales experience (in Months) and the number of computers sold during the previous month by 7 sales persons
Experience 4,12,9,6,10,30,7
Sales 19,42,28,31,39,30,21

using minitab output write the straight line (least squares) equation and the coefficient
The regression equation is Sales = 27.2 + 0.252 exp

Predictor Coef SE Coef T P
Constant 27.195 5.781 4.70 0.005
Exp 0.2517 0.4201 0.60 0.575

s=8.97833 R-Sq=6.7%

so this is where I am
4,6,7,9,19,12,30 I know the yis 27.195 and slope is 0.252
19,21,28,30,31,39,42

X Y Product
4-9=-5 19-30=-11 55
6-9=-3 21-30=-9 27
7-9=-2 28-30=-2 4
9-9=0 30-30=0 0
10-9=1 31-30 =1 1
12-9=3 39-30=9 27
30-9=21 42-30=12 252

55+27+4+0+1+27+252=366

(n-1)*sx*sy =correlation coeficient

correlation = 0.82385 So now how do I get the straight line equation? y=mx+b so 27.195=(.25175) (????)+27.19512
c)The I need to calculate 2 points to draw line on graph and give calculations.
d)Interpet what the slope means in term of the problem.
e)Identify a possible outlier, remove it and recalculate the new least squares line.
f)using my equation from (e)predict the number of sales for a person with 15 months experience.
g)can this model determine sales targets.
Click to expand...
Sue

I shall try repeating the gist of what I said before.

Experience is your X variable. Sales is your Y variable. (At least they should be if you set things up in your regression software properly.)

Conventionally, X is the independent variable and Y the dependent variable. Greater sales per month may be the result of greater experience, but cannot cause greater experience.

Once you have the equation, which is a linear equation, you can graph it by putting ANY two convenient values for X into the equation and calculating the appropriate values for Y from the equation. In practice what is least likely to lead to errors is to choose the smallest and largest values of X and calculate the associated Y values. Mark these two X, Y pairs on graph paper. Use a ruler to draw a line that joins those two points.

You seem to be complicating something that is very straight forward. It is hard for me to figure out what help to give you because I cannot imagine what your problem is. You do know how to graph a linear equation, don't you? If so, where or what is the difficulty?
 
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I give up on this question as I can not seem to understand where the 2 points come from. If I just choose from X and y then where do calculations come in.
I guess I'm not understanding the whole concept and how to plot. I thought I needed to find the coefficent so I figured that out. the straight line equation is
y=mx=b so I thought y was 27.195. Maybe I'm over analzing this question but when I'm confused and don't know what i'm doing I tend to do this. Thinking taking an online course was the mistake as there is no instruction just me reading and trying to figure things out.
 
Sue0113 said:
I give up on this question as I can not seem to understand where the 2 points come from. If I just choose from X and y then where do calculations come in. CHOOSE x AND CALCULATE y.
I guess I'm not understanding the whole concept and how to plot. I thought I needed to find the coefficent so I figured that out. the straight line equation is
y=mx=b so I thought y was 27.195. Maybe I'm over analzing this question but when I'm confused and don't know what i'm doing I tend to do this. Thinking taking an online course was the mistake as there is no instruction just me reading and trying to figure things out.
Click to expand...
y = mx + b = 0.2517*x + 27.195
where x is "Experience" and y is "Sales."
The parameters "m" and "b" come directly from the minitab output. Given any x, use this equation to find y.

ANY two points will define a line, so your choice of x is completely free. Plot the two points (as precisely as you can) then use a ruler to draw the line through those two points. The easiest point to calculate is x=0. The other point should be as far from x=0 as is convenient .. the farther away, the better the precision of drawing the line with a ruler. Try x=40.

That straight line is your regression fit - in the least-squares sense it is the "best" line to represent the data points. On this same graph you should plot the seven data points:
Experience 4,12,9,6,10,30,7
Sales 19,42,28,31,39,30,21
Does the line look like a good representation of the data?
 
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