With the Texas Instruments TI-82, you can calculate the most commonly-used descriptive statistics for one variable (mean, standard deviation, sum of values, sum of the values-squared, 5-number description) and for regression/correlation between two variables (regression coefficient and intercept, correlation coefficient). There are also options for other (non-linear) forms of regression.
You can also use the calculator to make plots (histogram, boxplot, scatterplot) of data you have entered.
Data are entered and stored in a table
(which allows checking that you have entered correctly & keeps
the numbers for recalculation)
For all statistical functions: Press STAT to see the first
statistics menu, then EDIT for data entry (or to clear data) or
CALC (for calculation)
The TI-82 has six lists which can be used for entering data. 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 from any list in which you will enter data, or your results will be messed up:
To clear a list: Press STAT, (EDIT is highlighted), 1[Edit], use the up cursor to highlight the label (L1,L2 or whatever) of the column, press CLEAR and then ENTER. [you are then ready to enter data]
A. One Variable:
Press STAT, (EDIT is highlighted), 1[Edit]
Values for one variable go in one column - use the cursor keys to move to the first entry in the column you choose, enter the number (you see it at the bottom of the screen), press down-arrow, enter the next, etc.
To change a value already typed in: Use the up & down arrows to highlight it, enter the new number & press the down-arrow or ENTER to put the new number in.You need to remember which column contains your data [especially if you have entered several columns of data]
B. One Variable, with frequencies
[Also can be used for calculations with a discrete variable whose distribution is given by a table]
Press STAT, (EDIT is highlighted), 1[Edit]
Values go in tone column, frequencies in another- enter the number (you see it at the bottom of the screen), press down-arrow, enter the next, etc. It is easiest to enter the values (x's) first and then the frequencies. Frequencies must be whole numbers (not decimals or fractions).
To change a value already typed in: Use the up & down arrows to highlight it, enter the new number & press the down-arrow or ENTER to put the new number in.
If you are entering data from a grouped data table (or histogram) use the class midpoint for value, class frequency as frequency.
You need to remember which column holds values and which column holds frequencies.C. Two variable
[For paired data of either sort - matched pairs experiments/observations or predictor/respone (x/y) data]
Press STAT, (EDIT is highlighted), 1[Edit]
Values go in pairs : x values (values of the predictor) in one column, y-values (values of the response) in another (it's easiest to enter all x-values down the column, then y-values down their column, next to corresponding x-values) [For paired-data: values from one group in one column, values from the second group - in maching order - in another]
You will need to remember which column holds x-values and which holds y-values.
A. One-variable
Press STAT, highlight CALC, press 1[1-Var Stats] (command 1-var stats appears on screen), then the column number [column numbers are obtained with 2d - number (2nd, 1 gives L1, 2d, 2 gives L2, etc), then ENTER
You see a screen with mean( x-bar), sum of x's sum of x-squares ( not "sum of squares" SS(x)) sample standard deviation (Sx) population standard deviation [not much use] and sample size (n) - scrolling down will show minimum, maximum, 1st & 3d quartiles and median [5-number description]
B. One-variable with frequencies
Press STAT, highlight CALC, press 1[1-Var Stats] (command 1-var stats appears on screen), 2nd-number[number of the values column] , [a comma - key is above the numbers], 2nd-2[L2], then ENTER
You see a screen with mean( x-bar), sum of x's, sum of x-squares ( not "sum of squares" SS(x) ), sample standard deviation (Sx) population standard deviation [not much use] and sample size (n) - scrolling down will show minimum, maximum, 1st & 3d quartiles and median [5-number description]
C. Two-variable
Regression/correlation
Press STAT, highlight CALC, press 5[LinReg(ax+b)] (command appears on the home screen) 2nd-number (of column for x's), [a comma - key is above the numbers], 2nd-number (of column for y's), then ENTER -
You see screen giving a (coefficient), b (intercept) and r (correlation coefficient) (also shows form of equation: y = ax + b, so you can see which number is which)
After you calculate the equation, you can define one of the graphing functions (Y1, Y2 etc.) for the regression line: Pres Y= and highlight a vriable that is not defined (can use "clear" to remove a definition) then (with the cursor on this line) press VAR, select 5:Statsitics, select EQ andfinally select 7: RegEQ - the regression equation will be pasted in to the line you chose.
Combined statistics
Press STAT, highlight CALC, press 2[2-Var Stats] 2nd-number (of the x-column), [a comma - key is above the numbers], 2nd-number (of the y-column)
You to see a screen giving mean of data in x-list (x-bar), sum of x-list data ( sum of x's) sum of x-squared ( not "sum of squares" SS(x)) sample standard deviation for x-list (Sx), then same data for y-list (called y on screen) and the sum of the xy's .
The TI-82 will produce four different types of plots, and up to three different plots can be defined [each can be turned on or off once it is defined]
To define a plot
Plots are defined using the "Statplots" options.
Press 2nd - Y= [STAT PLOTS] and you see a list. The information shown with this list shows: whether the plot is turned On or Off [is displayed on the graphing screen or not], the type of plot [shown with a symbol] the column [or columns] used for data and the graphing symbol (box, plus sign or point).
Select a number (1 to 3) for the plot you want to define [options 4 & 5 turn all plots on or off at once].
For the plot you are defining, you select several options either by highlighting the choice or by typing your choice.
To turn the plot On/Off - highliight your choice & press ENTER. Cursor down to select type.
To select type: use right/left cursor to highlight type, press ENTER to make highlight your choice, then press ENTER
The choices of types: Scatterplot,Scatterplot with points connected in order (from the list-will not be inorder of x's or y'sunless you sorted lists), basic boxplot (whiskers go to largest & smallest values), histogram,
The choices you must make depend on the type of plot:
For scatterplot and connect-line scatterplot - must select x-list and y-list
For boxplot & histogram: select data list for "Xlist" [then press ENTER]. If frequencies are used (as in I.B above), enter the name of the frequncy list for "Freq:" - otherwise you should enter 1 [then press "ENTER"]
Select graphing symbol as "Mark" by highlighting & pressing "ENTER" (default is a box - it works fine)To show the plot, with the plot turned on, press ZOOM and select 9:ZoomStat to get a window sized to show your plot.. [If some of the functions were turned on in the "Y=" list, they will also graph, which can be distracting].
Note:
If you have two or more plots turned on, they will all graph at once. If you have two boxplots turned on, they will appear one above the other. (side-by side boxplots - but horizontal)
You can control the window size and the spacing on a histogram with the "window" key - the "xscale" option is the class width.
The trace function can be used with statplots - giving coordinates of points (scatterplot), min & max (class limits) and frequency (n) for each bar in a histogram [notation a bit odd - be careful], min Q1, median, etc. for boxplot.
If you define a scatterplot , calculate the regression line with the same data and define Y1 to be this line, you can see the line with the scatterplot.
Errors or questions? Please let me know: cpeltier@saintmarys.edu
Last update 8/7/2000