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:
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Press [ON] key a couple to times
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Press [Right Shift] [5] (STAT) and select {3. Fit data..} to access FIT DATA Form
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Press soft key {PRED} to access PREDICT DATA Form (see Screen 3)
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Use the [Down] key a couple of times to move to X:
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Enter 0 and press [ENTER]
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The cursor with hop to Y: field
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Press soft key {PRED}
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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):
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Use the [Down] key a couple of times to move to X:
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Display PREDY(
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Enter 1 and press [ENTER]
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Display 89,455.5587629 is the Answer.
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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:
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Press [ON] key a couple to times
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Press [Right Shift] [5] (STAT) and select {3. Fit data..} to access FIT DATA Form
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Press soft key {PRED} to access PREDICT DATA From
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Use the [Down] key a couple of times to move to X:
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Enter 5400 and press [ENTER]
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The cursor with hop to Y: field
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Press soft key {PRED}
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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:
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Press [ON] key a couple to times
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Press [Right Shift] [5] (STAT) and select {3. Fit data..} to access FIT DATA Form
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Press soft key {PRED} to access PREDICT DATA From
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Use the [Down] key a couple of times to move to Y:
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Enter 125,000 and press [ENTER]
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The cursor with hop to X: field
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Press soft key {PRED}
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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.
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Press [Left Shift] [2D/3D] to access PLOT SETUP Form. (see Screen 1)
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Choose the Scatter Chart.
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Press [Left Shift] [WIN] to access PLOT WINDOW Form. (see Screen 2)
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Press the top soft key {AUTO} [F4] button.
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Press the top soft key {DRAW} [F6] button.
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This will display all the points (see Screen 3).
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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.