difference between planned and post hoc comparisons, which is the stroger of the two?
Solution
Testing this hypothesis is rarely the reason you did the experiment. Instead, you want to look
within the data, comparing this group with that group... So you want to make multiple
comparisons. There are several ways you can do this:
All possible comparisons, including averages of groups. So you might compare the average of
groups A and B with the average of groups C, D and E. Or compare group A, to the average of
B-F. Scheffe\'s test (not currently offered by any GraphPad program) does this.
All possible pairwise comparisons. Compare the mean of every group with the mean of every
other group. Prism and InStat can do these comparisons with Tukey or Newman-Keuls
comparisons.
All against a control. If group A is the control, you may only want to compare A with B, A with
C, A with D... but not compare B with C or C with D. Prism and InStat do this with Dunnett\'s
test
Only a few comparisons based on your scientific goals. So you might want to compare A with B
and B with C and that\'s it. Prism and InStat use Bonferroni\'s test for this.
The terminology is not always used consistently.
Multiple comparison test applies whenever you make several comparisons at once. This is in the
case in all four situations above.
Post test is generally used interchangeably with multiple comparison test, so applies to all the
situations above.
Post-hoc test is used for situations where you can decide which comparisons you want to make
after looking at the data. You don\'t need to plan ahead. Scenario I above clearly is post-hoc
testing. Scenarios II and III above require that you make some decisions (based on your scientific
goals). If you compare all pairs of means, you have decided not to do the more general
comparisons listed in part I. If you choose to compare all against the mean, you\'ve decided on
scientific grounds not to compare treatment groups with each other, but only to compare each to
the control. Because the use of these tests require some decisions that you should make before
seeing any data, choices II and III are not strictly post-hoc tests, but that term sometimes gets
used anyway
Note: The term \'post hoc\' means you can decide after the experiment..
Call Girls in Dwarka Mor Delhi Contact Us 9654467111
difference between planned and post hoc comparisons, which is the s.pdf
1. difference between planned and post hoc comparisons, which is the stroger of the two?
Solution
Testing this hypothesis is rarely the reason you did the experiment. Instead, you want to look
within the data, comparing this group with that group... So you want to make multiple
comparisons. There are several ways you can do this:
All possible comparisons, including averages of groups. So you might compare the average of
groups A and B with the average of groups C, D and E. Or compare group A, to the average of
B-F. Scheffe's test (not currently offered by any GraphPad program) does this.
All possible pairwise comparisons. Compare the mean of every group with the mean of every
other group. Prism and InStat can do these comparisons with Tukey or Newman-Keuls
comparisons.
All against a control. If group A is the control, you may only want to compare A with B, A with
C, A with D... but not compare B with C or C with D. Prism and InStat do this with Dunnett's
test
Only a few comparisons based on your scientific goals. So you might want to compare A with B
and B with C and that's it. Prism and InStat use Bonferroni's test for this.
The terminology is not always used consistently.
Multiple comparison test applies whenever you make several comparisons at once. This is in the
case in all four situations above.
Post test is generally used interchangeably with multiple comparison test, so applies to all the
situations above.
Post-hoc test is used for situations where you can decide which comparisons you want to make
after looking at the data. You don't need to plan ahead. Scenario I above clearly is post-hoc
testing. Scenarios II and III above require that you make some decisions (based on your scientific
goals). If you compare all pairs of means, you have decided not to do the more general
comparisons listed in part I. If you choose to compare all against the mean, you've decided on
scientific grounds not to compare treatment groups with each other, but only to compare each to
the control. Because the use of these tests require some decisions that you should make before
seeing any data, choices II and III are not strictly post-hoc tests, but that term sometimes gets
used anyway
Note: The term 'post hoc' means you can decide after the experiment.
