1. Make Sure You Have Your Dependent Variable and Factor Selected
Now Left
Click on
Options

2. The Options Menu Comes Up
Left click the
Boxes to check-off
What you want
Descriptive Stats
Homogeneity of
Variance Test
Means Plot
Then left click
continue

3. Why the Crud Would I Pick Those Tests?
Your ANOVA appears to say that the fly ash addition does not change pavement durability – yet your field people say otherwise.
The data for a valid ANOVA test meets the assumptions of ANOVA
One of the assumptions is that the variance of each different treatment is the same (or nearly so).
You picked descriptive statistics which will tell you the standard deviation of each treatment
You also picked a test called the homogeneity of variance test which will check to see whether differences in variances are large enough to indicate a problem
Finally you ask the computer to show you the means of each treatment.

4. Now You Have Set Your Options, Just Click Ok like before to run your test

5. Out Comes the Data – This Time With Extras

6. The Descriptive Stats Show You The Standard Deviation of Each Treatment
These standard deviations are suppose to be
About the same. Are they?

7. Here is Your Homogeneity of Variance Test
The null hypothesis is that all variances are the same
Rejecting the null hypothesis means you believe they are different
Your test statistic was – What are the chances of getting a more far out
Value than that?
What does that tell you about your alpha level if you reject the null hypothesis?

8. Heres’ the Plot of the Means
As you move from 1
(no fly ash) to 5
(100% fly ash) does it
Look like anything is
Happening to the
Strength?

9. But What Does the ANOVA Test Say?
The null hypothesis is that fly ash addition does not change the pavement
Strength
Rejecting the null hypothesis would mean that it does.
What is our alpha level if we reject the null hypothesis?

10. Our

11. Our Descriptive Statistics Let Us Look at the 95% confidence interval for strength of each type of concrete
Does any type of
Concrete stand out from
The crowd to where
The confidence
Intervals do not
Overlap?
Do you have any idea
Why the ANOVA test
Does not reject the
Null hypothesis?

12. But is the Test Valid?