With the Texas Instruments TI-81, you can calculate the most commonly-used descriptive statistics for one variable (mean, standard deviation, sum of values, sum of the values-squared) and for regression/correlation between two variables (regression coefficient and intercept, correlation coefficient)
Data are entered and stored in a list (which allows
checking that you have entered correctly & keeps the numbers for recalculation)
For all statistical functions: Press 2nd - MATRIX [STAT] to see the
statistics menu
There are three situations in which you enter data - one variable (actual data), one variable (with frequencies - grouped or ungrouped), two variable. Always clear old data before entering new data, or your results will be messed up:
Press 2nd-MATRX[STAT], highlight DATA (did you
clear old data?), choose 1[Edit] to get in position to enter data.
Values go in as x- values (x1, x2 . . .) - the y1, y2 remain as 1's (enter
each value & press down arrow twice to jump to next x)
To change a value already typed in, use up/down arrow to highlight it, press
CLEAR, then enter new value
Press 2nd-MATRX[STAT], highlight DATA (did you
clear old data?), choose 1[Edit] to get in position to enter data.
Values go in as x- values (x1, x2 . . .) - frequencies are entered as y
-( y1 is frequency of first value, etc.)(enter each value & press down
arrow )
Frequencies must be whole numbers (not decimals or fractions)
To change a value already typed in, use up/down arrow to highlight it, press
CLEAR, then enter new value
Press 2nd-matrix[STAT], highlight DATA (did you
clear old data?)
Each pair goes in as an (x, y) pair: (x1, y1) then (x2, y2) etc.
Press 2nd-matrix [STAT], 1[1-var] then ENTER - you will see a screen with mean( x-bar, sum of x's sum of x-squareds (not "sum of squares" SS(x)) sample standard deviation (Sx) population standard deviation [not much use] and sample size (n - the sum of the y's) .
Press 2nd-MATRX [STAT] leave CALC highlighted, press 2 [LinReg] then ENTER,-you will see a screen which gives a (intercept) b (slope) and r (correlation coefficient). [You might want to write on your calculator, or on the inside of the cover, something like a=int, b=slope, because the screen does not tell which is which]
Errors or questions? Please let me know: cpeltier@saintmarys.edu
Last update 7/20/98