I have recently sent a paper on aflatoxin levels in nuts for publishing. The aim of the study was to analyze a total amount of 106 nuts. The nuts were divided into four categories: walnuts (n=33), hazelnuts (n=19), pistacchio (n=29) and almonds (n=25). The reviewer seems not to have a broad knowledge on study design and statistical analysis, which can be seen in his critique: "In my opinion, every sample should be equal in size, in order to improve the quality of the research." I totally disagree with his opinion, mostly because following statistical analysis did not require the same sample size. This was a cohort epidemiological study, not a experimental one. Can somebody back me up with references or explain in details why do i don't need equal sample sizes to do a high quality research?
Or in other words: Would the research be better if i compared 4 categories with the same sample size (eg. walnuts=23, hazelnuts=23, almonds=23, pistacchio=23), compared to my sample sizes?