I have a sample that is very left skewed. The mean of this sample is 4.01 (min = 1, max = 5). I would like to know whether or not a subset of this sample is significantly different than the sample as a whole.
My use case:
I want to take a portion of this sample (344 of the 1140 responses) and use Welch's t-test to determine whether the mean of the subset is significantly different than the mean of the entire sample.
- Am I correct in assuming that significance should not be measured (at least not using Welch's t-test) if your data is extremely skewed?
- Is there a way to determine statistical significance between a sample and a subset of that sample when the data is skewed?
All of my computations are in php, as I am a web developer. So if your answer involves using some sort of statistical software magic I won't have a clue what you're talking about...thanks in advance!