Hello,

I have two questions here.

RESOLVED (for now): You perform the bonferroni for multiple tests and/or multiple comparisons.

FIRST: I have performed 4 mixed between-within subjects ANOVAs, that look at the differences between time (2 time points) and group (2 groups). I have been told in some places that you divide you alpha level by the amount of tests you're running, but in the below quote from Pallant 2011 is says "comparisons" rather that "tests", and it has me wondering whether, with 4 mixed between-within subjects ANOVAs looking at time points and group differences, do I need to divide the alpha level by 4 or by 8?

SECOND: If I'm reporting confidence intervals with the rest of my output, is there anything I need to do with them, any adjustments, etc, any calculations for the confidence intervals, relating to the Bonferroni adjustment. I know that for the Bonferroni adjustment I am examining my p values according to the adjustment (in this case I think it's: 0.0125/0.013), but is there anything different I need to do when reporting the confidence intervals?

I have searched the forum, looked in my textbooks, but there I can't find a clear (to me) answer. Thank you for your help.

"The other alternative is to apply what is known as a Bonferroni adjustment to the alpha level that you will use to judge statistical significance. To achieve this, you can divide your alpha level (usually .05) by the number of comparisons that you intend to make, and then use this new value as the required alpha level. For example, if you intend to make three comparisons the new alpha level would be .05 divided by 3, which equals .017."

I have two questions here.

RESOLVED (for now): You perform the bonferroni for multiple tests and/or multiple comparisons.

FIRST: I have performed 4 mixed between-within subjects ANOVAs, that look at the differences between time (2 time points) and group (2 groups). I have been told in some places that you divide you alpha level by the amount of tests you're running, but in the below quote from Pallant 2011 is says "comparisons" rather that "tests", and it has me wondering whether, with 4 mixed between-within subjects ANOVAs looking at time points and group differences, do I need to divide the alpha level by 4 or by 8?

SECOND: If I'm reporting confidence intervals with the rest of my output, is there anything I need to do with them, any adjustments, etc, any calculations for the confidence intervals, relating to the Bonferroni adjustment. I know that for the Bonferroni adjustment I am examining my p values according to the adjustment (in this case I think it's: 0.0125/0.013), but is there anything different I need to do when reporting the confidence intervals?

I have searched the forum, looked in my textbooks, but there I can't find a clear (to me) answer. Thank you for your help.

"The other alternative is to apply what is known as a Bonferroni adjustment to the alpha level that you will use to judge statistical significance. To achieve this, you can divide your alpha level (usually .05) by the number of comparisons that you intend to make, and then use this new value as the required alpha level. For example, if you intend to make three comparisons the new alpha level would be .05 divided by 3, which equals .017."

Last edited: