Scatter plots and predictions?

Question

table shows sales of 8 sales men during given time period:

amt sales-yrs of experience

$9000----6

$6000----5

$4000----3

$3000----1

$3000----4

$5000----3

$8000----6

$2000----2

qestions-

1. draw scatter plot-(should this be straight line)?

2. write prediction equation

3. predict sales for 8 yrs of experience

4. predict yrs of experience for selling 7300

Answer 1

b = Σx[i]-xbar)*(y[i]-ybar) / sqrt[Σ(x[i]-xbar)^2 Σ(x[i]-xbar)^2]

regression coefficient is 1191.4894

a = ybar - b*xbar

Constant a is 531.9149

2)Prediction equation: y = 531.9149+1191.4894x

y - sales x = years of experience

3)when x=8, y=sales = 531.9149+1191.4894(8)=10063.8301

You can write sales with 2 decimal digits as they are dollar amounts.

4)Predict x when y=7300

7300 = 531.9149+1191.4894x

solve for x =5.68 years (5 years 8 months)

--------years-------sales------------p... sales

         6.0000      9000.0000      7680.8511

         5.0000      6000.0000      6489.3617

         3.0000      4000.0000      4106.3830

         1.0000      3000.0000      1723.4043

         4.0000      3000.0000      5297.8723

         3.0000      5000.0000      4106.3830

         6.0000      8000.0000      7680.8511

         2.0000      2000.0000      2914.8936

Answer 2

a scatter plot is where you have the X and Y axis and you draw crosses in there right place ( you go across the bottom and read across and draw a cross / plot )

Answer 3

You don't say what tools/methods you're supposed to use. The easiest way is to just put it in Excel, and let it do it.

For a manual chart, let the X axis represent experience (range of 0-$10,000, marked in $1,000 increments). Let the Y axis represent sales (range of 0 to 10 years, marked in 1 year increments.) Then mark every intersection of experience/sales.

Since there are two different sales volumes for 6 years of experience and also for 3 years, the line can't be straight.

Sorry, but I won't do the regression by hand. Excel says it's 1191.5x + 531.91