48 Section 3: Numeric Functions
production (a “known” x-value) for 1977 and presses ´j. Because the
correlation coefficient for Voltz's data is automatically included in the
calculation, she can view how closely her data it a straight line by simply
pressing ® after the ŷ prediction appears in the display.
Keystrokes Display
7.142
7.142
Voltz’s estimate of 1977
electrical output.
´j
2.005
Predicted coal
production for 1977.
®
0.921
The original data closely
approximate a straight
line.
Conversely, suppose Voltz wishes to estimate the electrical output should there
be a future drop in coal production to 1.800 billion metric tons.
Keystrokes Display
1.8
1.8
Hypothetical future coal
production.
´ª
5.951
Predicted electrical
output for that year.
®
0.921
Again, the correlation
coefficient for the
original data.
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