Post-hoc versus Planned Comparisons

Post hoc versus planned comparisons

Understanding the difference between post hoc and planned comparisons can often be confusing. The confusion stems from the fact that both are used in identical sittuations. They both are done after the analysis has come back as having significant results. the main difference between the two actually lies within name planned comparisons is when the researcher a priori declares which analysis the run if there is significance found specifically where they're going to look for further differences to occur in between which specific groups. whereas with post hoc you're just looking for any difference to occur.

The difference between these two can be thought of as planned comparisons has a little bit more scientific rigor and reduces the type error probability. Because the researchers are just not looking for any random differences. Rather they are basing it off of theoretical differences that should occur. This View is based on more of the social science experimenter view versus a data science view.

More specifically if you were to think about it like going shopping. If you're going shopping with a shopping list you know what you're looking for this is the equivalent of planned comparisons because you are planning out what you are going to buy ahead of time. going shopping without a shopping list  would be the equivalent of a post hoc where you only buy things that are on sale but you're just looking for anything on sale. You could end up going home with 500 rolls of toilet paper that's because they were a good deal.

in conclusion post hoc and planned comparisons are both useful they serve the same purpose in finding out where exactly differences occur as a follow-up test. However  planned comparisons are often viewed as Superior because they are reducing are type 1 error  and have more scientific rigor.