Part II
Another type of graph is a Bar Chart (Cell Plot). Bar Charts are use to show the means for a variable of your choice split by some nominal variable.
Problem #1: There is a sample data file called "Lipid Data" in the CS130 Public folder. I would like you to take this file and produce a Bar Chart showing the mean weight of the people in the file split by Gender. Also make a plot of the mean Cholesterol split by Gender. These two plots really allow us to examine one variable of interest.
What if we want to examine the relationship between two variables.?
In statistics, we can define two types of variables:
(1) independent - "it is what it is" and nothing influences it (e.g. Gender)
(2) dependent - most likely dependent on another variable (e.g. Cholesterol may be dependent on age)
Consider the following table which shows the number of bushels of wheat produced for the given rainfall amounts:
Rainfall 2.5 3 4.5 7.6 9.5 10.3 in inches
Bushels 37 43 42 46 48 51 of wheat
Problem #2: Create a scatterplot (scattergram) for this data. You need to correctly set up the data in a SPSS Dataset and then graph the data correctly by deciding which variable is the dependent variable and which is the independent variable.
Problem #3: Least Squares Regression is a technique used to find from the data, the equation of the best line that fits through the scattergram. In essence, we want to find a line of the form y = mx + b for the given data. We have used the various regression analysis tools from Excel, so let's now try and use them in SPSS. Find a linear regression for the above data and predict the number of bushels of wheat that would be produced for a rainfall amount of 6.2 inches.