Calculator resources and instructions  (Page 4/4)

Getting started

Create the folder “ mystat ” (for statistics):

• Press 2nd VAR-LINK . Press F1 Manage .
• Press 5:Create Folder . Enter the name “ mystat ” and press Enter twice.

Make mystat your current folder:

• Press MODE . Arrow down to Current Folder and arrow over and down to mystat .
• Press Enter twice. You should see the name MYSTAT in the lower left corner.

Creating list names L1 , L2 , and L3 :

• Press APPS 1:Flashapps . Press Enter .
• Arrow up into the name area of the lists and over until you reach a blank title area.
• Press L (above the 4 ). Press alpha . Press 1 . Press Enter .
• Arrow up into the name area of the lists and over until you reach a blank title area.
• Press L . Press alpha . Press 2 . Press Enter .
• Arrow up into the name area of the lists and over until you reach a blank title area.
• Press L . Press alpha . Press 3 . Press Enter .

Linear regression

Given the data set: (3, 5), (6, 8), (9,7), (5, 20). The xlist is 3, 6, 9, 5 and the ylist is 5, 8, 7, 20. Put the xlist into L1 and the ylist into L2 .

Constructing a scatter plot

• Make sure you are using Flashapps (Press APPS 1:Flashapps . Press Enter .)
• SCATTERPLOT: After you are have entered your lists in L1 and L2 , press F2 .
• Press 1:Plot Setup . Highlight Plot 1 and make sure there are no checks next to any other plots. If there are, arrow to the plot and press F4 .
• Then arrow back to Plot 1 .
• Press F1: Define . For Plot Type , press the right arrow and press 1:Scatter .
• Arrow down, press the right arrow and press 1:Box .
• Arrow down to x . Press alpha L1 . Arrow down to y and press alpha L2 .
• Arrow down to Use Freq and Categories? and use the right arrow. Highlight NO and press Enter .
• Press Enter again.
• Press F5 Zoomdata . You should see the scatterplot. Press F3 to trace and the arrow keys to see the coordinates of the points.

Calculating the regression equation

• Press APPS , 1:Flashapps , and Enter .
• Press F4:Calc .
• Press 3:Regressions .
• Press 1:LinReg (ax+b) . For x List , enter alpha L1 . Arrow down. For y List , enter alpha L2 .
• For Store RegEqn to: , arrow right and arrow down to y1(x) (or any one of the y's) and press Enter .
• Press Enter . You should see a screen with a , b , r^2 , and r on it. The regression is complete.
• Write down the equation from the information and press Enter .
• The linear regression is yhat = 11.2267 - .2133x

Drawing the regression line

• Press the key with the green diamond on it (it is below the 2nd key) and press Y= (above the F1 key).
• This is the Line of Best Fit .
• Press the key with the green diamond on it and press GRAPH (above the F3 key). The line will be drawn.

Outliers

• When you do Linear Regression, a list called " resid " is created automatically.
• This list has the “ y – yhat ” values in it.
• Go into Flashapps and into your lists.
• Arrow to " resid " so you see it.
• Then, arrow to the list name L3 . Press F3 .
• Press 1:names . Arrow down to STATVARS . If it is not checked, press F4 .
• Then, arrow down to resid . Press Enter . Press ^2 . Press Enter . L3 will have the (y - yhat)^2 values.
• Press HOME and Press F1 8 to clear it.
• Press 2nd MATH . Press 3:List . Press 6:Sum . Press alpha (L3) .
• Depending on how you have MODE Display Digits set, you should see approximately 137.1467. This is the SSE.
• Calculate $s$ . (You should be HOME .) Press clear .
• Press the square root symbol and enter 137.1467/2 . (You get the denominator by taking the number of data points and subtracting 2: $\text{4 - 2 = 2}$ .)
• Press Enter . You should see 8.2809 (to 4 decimal places).
• Press the times key and enter 1.9 . Press Enter . You should see 15.7337 .
• Press clear . Press 2nd VAR-LINK .
• Arrow down to resid (it is below STAT VARS ). Press Enter . Press Enter again.
• Arrow up to the list. Scroll through the list using the arrow keys.
• Compare 15.7337 to the absolute values of the numbers in the list. If any absolute value is greater than or equal to 15.7337, then the corresponding point is an outlier.
• Absolute values of the numbers in the list are approximately 5.59, 1.95, 2.31, 9.84.
• None of them are greater than or equal to 15.7337.
• Therefore, for this data set, no point is an outlier.