Publications by Richard Morey

How to check Likert scale summaries for plausibility

Suppose you are reading a paper that uses Likert scale responses. The paper reports the mean, standard deviation, and number of responses. If we are — for some reason — suspicious of a paper, we might ask, “Are these summary statistics possible for this number of responses, for this Likert scale?” Someone asked me this recentl...

9683 sym 4 tbl

Numerical pitfalls in computing variance

One of the most common tasks in statistical computing is computation of sample variance. This would seem to be straightforward; there are a number of algebraically equivalent ways of representing the sum of squares \(S\), such as \[ S = \sum_{k=1}^n ( x_k – \bar{x})^2 \] or \[ S = \sum_{k=1}^n x_k^2 + \frac{1}{n}\bar{x}^2 \] and ...

5904 sym R (1814 sym/10 pcs)

Numerical pitfalls in computing variance

One of the most common tasks in statistical computing is computation of sample variance. This would seem to be straightforward; there are a number of algebraically equivalent ways of representing the sum of squares (S), such as [ S = sum_{k=1}^n ( x_k – bar{x})^2 ] or [ S = sum_{k=1}^n x_k^2 + frac{1}{n}bar{x}^2 ] and the sample ...

5838 sym R (1814 sym/10 pcs)