ANOVA 1: Calculating SST (total sum of squares) | Probability and Statistics | Khan Academy

Analysis of Variance 1 - Calculating SST (Total Sum of Squares)

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[wyn]

I recall that for chi square, the degrees of freedom was (m-1)(n-1). I don't understand why this should be different.

[BigGulp]

Disclaimer - the "mean of means" (average of multiple means) is only = to the grand mean (average of all data points) when each group has the same number of data points (in this case they all have three).

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[vman]

Great video (as always with Khan Academy) BUT the mean of means in general is not equal to the grand mean. For them to be equal, you need to have the same number of data points in each group. Otherwise, you must calculate the grand mean by simply averaging together all the values in all the groups.

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[alkalait]

Finally I have an intuitive sense of why computing the sample variance of a dataset involves dividing the sum of squared distances from the sample mean by N-1. Thank you.

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