# Linear Regression

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### #1 sanderson

sanderson

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Posted 01 January 2009 - 03:31 PM

Hi Folks

Happy New Year

IÂ´d like to know how to predict the future with this problem:
Say, a company started business in 1972, and IÂ´ve been watching its growth fairly closely.
Its profits for successive years have been:

Year Profits ( millions of dollars)
1972 -1.2
1973 -0.3
1974 2.1
1975 1.8
1976 2.7 what will I predict the profit level to be in 1978 and 1980?
1977 ? For what year will I predict profits of \$10 millions?
1980 ?

Please, show me how to calculate them and for a given y value what will be the x value with ClassPad 330 in Statistc mode.
Thank You.

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Posted 06 January 2009 - 03:55 PM

Hi Folks

Happy New Year

IÂ´d like to know how to predict the future with this problem:
Say, a company started business in 1972, and IÂ´ve been watching its growth fairly closely.
Its profits for successive years have been:

Year Profits ( millions of dollars)
1972 -1.2
1973 -0.3
1974 2.1
1975 1.8
1976 2.7 what will I predict the profit level to be in 1978 and 1980?
1977 ? For what year will I predict profits of \$10 millions?
1980 ?

Please, show me how to calculate them and for a given y value what will be the x value with ClassPad 330 in Statistc mode.
Thank You.

Go into the Stats application and enter your years in list1 and the profits in list2. Select Calc->Linear Reg, make sure XList is list1 and YList is list2, and I like to turn on the Copy Formula option. Then my formula can be found as y1 in the graph application. You can graph it, compute various values, etc. I was having some odd domain error, but after I changed the scope of my graphing window that seemed to go away.

### #3 Vulpes Virago

Vulpes Virago

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Posted 11 January 2009 - 03:09 PM

In the statistics application, enter your years in list1 and your profits in list2. Open the Calc menu and select Linear Reg. Make sure Xists is set to list1, YList is set to list2 andFreq is set to 1. Tap OK.
This process will calculate and store the a coefficient and b coefficient for the regression equasion y=a*x+b (in the system variables aCoef and bCoef). Y is your profit, and x is the year. The next step is to go to the numeric solver and type in the following equasion:
y=aCoef*x+bCoef
Highlight the radio button for x if you want to calculate the year, or y if you want to calculate the profit. Fill in the known variable and tap the Solve button.
This method has two advantages over graphing the equasion. First, the range of the graphing window does not matter- You can literally calculate any value within the calculator's range. The second is that the answers will be as exact as the calculator is capable of.
I hope this helps.

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