Follow.

Please explain what specifically you have done (what buttons you've clicked, what output you've seen, etc.) and what is missing. I don't understand what "significance letters" are.

Stephen Politzer-Ahles I am talking about these letters...present at the top of the bars.

I have used ANOVA in excel and it has provided me with a set of data but I don't know how to apply tukey's hsd in order to get these letters..

What do those letters refer to?

Whether or not there is a significance difference.

Whether or not there is a significant difference with what? I don't know what a, b, or c are.

Stephen Politzer-Ahles If, for example, 2 data bars share the same letter there is no significant difference between them. In the picture above, early, mid and late are not significantly different while "all" is significantly different from the rest.

It's not really clear whether you are asking how to add letters to a plot, or how to perform pairwise comparisons (to determine what those letters should be) with Tukey's HSD. For the latter question, all you need to do is Google, and you will find many tutorials (for example, https://www.spss-tutorials.com/spss-one-way-anova-with-post-hoc-tests-example/ and http://blog.excelmasterseries.com/2014/05/excel-post-hoc-tukeys-hsd-test-for-2.html are the very first results I saw when searching "tukey's hsd spss" and "tukey's hsd excel", respectively, and both appear to answer your question).

Yeah but what I am looking for is whether I use Tukey's HSD or LSD. My study has 2 factors i.e. antibiotics and organic amendment. 2 antibiotics with 2 doses..and 3 organic amendments with a single dose.