I have a poll data table with which be filled with between two and six thousand entries (one entry contains some 30 data). It is a table in SQL, a computer database language. The table will contain primarily numeric data.

I want to compute the correlation strengths between certain variables, for which I need to know whether their distribution is normal. I cannot use the normal distribution tests, because SQL has only a few native statistical functions, the most complicated being the population standard deviation. And I do not know enough about SQL to write complicated test codes myself. I have written the correlation formula code, but that is as far as my knowledge goes.

Instead, I want/have to compare the mean, median and modus, which should all be (more or less) equally positioned on the x axis in a normal distribution. But where lies the cut off point? When must I conclude that the distribution is not normal? Have difference percentages ever been established for that? Or is there an experienced statistician that could give me an educated guess?

I want to compute the correlation strengths between certain variables, for which I need to know whether their distribution is normal. I cannot use the normal distribution tests, because SQL has only a few native statistical functions, the most complicated being the population standard deviation. And I do not know enough about SQL to write complicated test codes myself. I have written the correlation formula code, but that is as far as my knowledge goes.

Instead, I want/have to compare the mean, median and modus, which should all be (more or less) equally positioned on the x axis in a normal distribution. But where lies the cut off point? When must I conclude that the distribution is not normal? Have difference percentages ever been established for that? Or is there an experienced statistician that could give me an educated guess?

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