statistics for "difference in differences"

[seraphin]

I wonder if anyone on this forum knows how to calculate using EXCEL the statistics for "difference in differences".

I have 4 sets of groups -
each group has a mean and a standard error
I am trying to calculate if the difference between group 1 and 2 is the same or not the same (statistically) from the difference between group 3 and group 4.

I can do student t, but not sure what statistics to use in EXCEL to calculate the difference in differences.

Any help?

 

[steve the fish]

You can do an ANOVA in excel if thats what you mean. That will tell you if your groups are the same statistically.

 

[seraphin]

Don't think ANOVA is applicable.
ANOVA can tell me if there are differences in the 4 groups.
But I need to get two numbers first - the difference in group 1 and 2. and the difference in group 3 and 4. (say height between group 1 and 2 and height between group 3 and 4).
Then I ask if the height difference between group 1 and 2 is different or not (statistically) from the height difference between group 3 and 4.

 

[steve the fish]

You could perform an ANOVA on the differences. Why you would use differences and not just the heights themselves?