1. The Empirical Rule indicates that the range from  - s up to  + s holds two-thirds of the distribution of any numerical variable.
2. If a distribution is bell shaped, then about 5% of the z-scores are larger than 1 or less than -1.
3. The removal of an outlier with z = 3.3 causes both the mean and the SD of the data to decrease.
4. The interquartile range of a distribution is half the range from the smallest to largest value.
5. If the standard deviation of a variable is 0, then the mean is equal to the median.
6. The variance of a variable increases as the number of observations of the variable increases.