1. Psychology 202a Advanced Psychological Statistics September 10, 2015

2. The plan for today Continuing the discussion of standard deviation. Descriptive statistics for skew and kurtosis. Linear transformations. Models. Conditional distributions.

3. The standard deviation (cont.) The conceptual formula for the sample variance is The standard deviation is just the square root of the variance.

4. Numerical assessment of skew ordering of mean and median skewness indices –Pearson proposed 3*(mean-median)/s –third moment: –comment on (lack of) utility of third moment

5. Numerical assessment of kurtosis fourth moment: bad idea except in very large data sets