STA10 Basic Statistics and Quantitative Literacy
Chapter 10-11
Name:
Group Projects: June 6, 2006
Relationships Between Numerical Variables
In this project we will be studying the relationship between a person’s height and weight. Our sample
will be a sample of convenience, the students in this classroom. Each student will write on a piece of
paper how much they weight (in lbs) and how tall they are (in inches). We will then collect the data
and analyze it using JMP IN.
Once the data has been collected we must enter it into JMP:
1) First to open JMP IN on the computer click on START\Programs\Mathematics and Stat\JMP
IN 5.1\JMP IN 5.1.
We will then be creating a new data table so under the JMP starter click on NEW
DATA TABLE.
2) To load our data, on the left hand side of the screen under columns, right click on column 1and
select COLUMN INFO. Name the column “Weight” all else should remain the same, and then
click OK.
3) You must now begin filling down the column, the class weight data. Make sure not to make
any mistakes when entering the data.
4) Repeat the above steps by right clicking on “Weight” and then choosing New Column and
name this one “Height.” Fill in this data but make sure that you pair the heights with the correct
weight (the person height should be placed directly across from their weight in the table!!!)
Now we can analyze the data using JMP.
1) On the top toolbar click on ANALYZE\Fit Y by X
2) When the new screen comes up we want to click on “Weight” and then the Y,Response button.
This will make “weight” our y-variable in our scatterplot. (the one that goes on the vertical
axis).
3) Now click on “Height” and then the X,Factor button. This will make “height” our x-variable in
our scatterplot. (the one on the horizontal axis of the plot) Then click on the OK button.
4) You should see a scatter plot of the two variables. Copy and Paste the scatter plot below, does
it seem that there is a strong correlation between Height and Weight? Does the correlation
appear to be positive or negative?
5) Next, to fit the regression line we click the red arrow to the left of the scatter plot and choose
“Fit Line”. We can now see that the least squares line (the one that minimizes the vertical
distances between the data points and the lines). Copy and Paste this new graph below. What
is the equation of the regression line? This can be found below the words “Linear Fit”
Weight = ____________ + ____________ Height
What is the intercept of the line and what is the slope?
Intercept:_________________
Slope:____________________
What is the interpretation of the slope? For example if the slope was .5 we would say
that if Height increased by one inch then we would expect weight to increase by .5 lbs.
(write a sentence of this form only using the actual slope that you found)
We can also use the regression line to predict values of weight given a person’s height.
(ONLY PREDICT if the height is within the given range) . Therefore, given that a
person is 66 inches tall what to we expect that they should weigh?
6) Next, to find the correlation coefficient this is under Summary of Fit under RSquare but is the
square root of this value. (However, if you see that the correlation should be negative you
should add a negative sign to the correlation coef. After taking the square root.) What is the
correlation coefficient?
We can interpret RSquare (the square of the correlation coef.) as the percentage of the
Y-variable that is explained by the X-variable. For example, if RSquare was .8 then we
would say that 80% of the variation in a person Weight is explained by the persons
Height. Write a sentence to interpret the RSquare that you found for this study.
Type your responses into the word document and print it out and turn it in by the end of class!!