1. Research to Improve Student Learning
ED 558

2. A problem…
Imagine that you give your students a spelling test and you do not give them back the results of the test.
Then, a month later, without teaching them anything about how to spell the words, you give them the same spelling test again.
Would you expect the scores on the two tests to be exactly the same?

3. A problem…
With people, things change even when we do not do anything to make those changes occur.
In statistical parlance, that is called random error—changes (variance) for which we can not account.
To statisticians this is not a problem. You just have to adjust for random error.

4. A new problem…
This time you will give the students the test but then give them lots of practice (work sheets) on spelling the words correctly.
Now, a month later you will give them the same test you originally gave them.
Now you can say how much each student improved because of the practice.
You can also say how much the group as a whole improved.

5. Group Differences
Statisticians are not interested in individuals very much except as sources of data.
So, think about the group as a whole. If you figure out what the average score was for the first test and then compare it to the average score for the second test you can figure out how much the students changed as a group.

6. Except…
You already know that the average score on the two tests will be different whether they did the work sheets or not—random error.
So, in order to know if the work sheets helped the students learn how to spell the words you would have to make a judgement.
The difference between the two tests is so big that it could not be accounted for by just random error.

7. Well, that makes things more complicated.
Questions that need answers:
When is the difference big enough that you can ignore the random error problem?
Since you are looking at numbers is there some way to do a numerical calculation that tells you if the difference is big enough?
If you figure out how to do this for the two spelling tests will that apply to all group comparisons?

8. The Course Gathering and summarizing information about groups
Calculating differences between groups
Using the right calculation for what you want to know
And then, writing about what you did

9. Gathering and summarizing information about groups
Step 1
Install EZAnalyze

10. Gathering and summarizing information about groups
Step 1
Install EZAnalyze
Step 2
Learn some basic stuff about Excel