Using HP 50g for Cost Estimation with Linear Regression

Entering data in HP 50g:

Press [Right Shift] [5] (STAT) and select {3. Fit data..} see Screen 1.

To access FIT DATA Form Press soft key {EDIT} (F1). Enter the data as show on see Screen 2.

Enter the the following into the Column 1
5,000
5,500
4,800
5,300
4,950
5,150

And into Column 2
120,000
122,100
118,540
122,400
119,100
124,200

What is Johnson’s fixed cost:

• Press [ON] key a couple to times
• Press [Right Shift] [5] (STAT) and select {3. Fit data..} to access FIT DATA Form
• Press soft key {PRED} to access PREDICT DATA Form (see Screen 3)
• Use the [Down] key a couple of times to move to X:
• Enter 0 and press [ENTER]
• The cursor with hop to Y: field
• Press soft key {PRED}
• Press soft key {EDIT} to display the number

It should show 89,449.3814433 which is the Answer. (see Screen 4)

Johnson’s variable cost (cost to build one chair):

• Use the [Down] key a couple of times to move to X:
• Display PREDY(
• Enter 1 and press [ENTER]
• Display 89,455.5587629 is the Answer.
• Deduct this with the above fixed cost 89,449.381

6.178 which is the cost for one unit of chair.

How good is the fit of the linear regression line generated?

Press [ON] to exit FIT DATA form (see Screen 5)
The Correlation will be displayed
It should show 0.716220427081
0 is worst and 1 is best, so 0.7 is fairly good.

Total costs for 5,400 chairs:

• Press [ON] key a couple to times
• Press [Right Shift] [5] (STAT) and select {3. Fit data..} to access FIT DATA Form
• Press soft key {PRED} to access PREDICT DATA From
• Use the [Down] key a couple of times to move to X:
• Enter 5400 and press [ENTER]
• The cursor with hop to Y: field
• Press soft key {PRED}
• Press soft key {EDIT} to display the number

It should show 122,806.907216 which is the Answer.

Total costs were $125,000, how many chairs:

• Press [ON] key a couple to times
• Press [Right Shift] [5] (STAT) and select {3. Fit data..} to access FIT DATA Form
• Press soft key {PRED} to access PREDICT DATA From
• Use the [Down] key a couple of times to move to Y:
• Enter 125,000 and press [ENTER]
• The cursor with hop to X: field
• Press soft key {PRED}
• Press soft key {EDIT} to display the number

It should show 5,755.02336448 which is the Answer.

With Graphing Calculator you can chart the above solution.

• Press [Left Shift] [2D/3D] to access PLOT SETUP Form. (see Screen 1)
• Choose the Scatter Chart.
• Press [Left Shift] [WIN] to access PLOT WINDOW Form. (see Screen 2)
• Press the top soft key {AUTO} [F4] button.
• Press the top soft key {DRAW} [F6] button.
• This will display all the points (see Screen 3).
• To draw the Linear Curve Fit press the top soft key {STATL} (see Screen 4).

This solution is also applicable to HP 49g, HP 49g+ Graphing Calculator.