The "g" loadings of mental tests are always positive and usually range between.10 and.90, with a mean of about.60 and a standard deviation of about.15.
When the distribution follows a log-normal curve (values expressed in decibels), the mean and standard deviation can be used to compute the medium-power talker.
Several are standard statistics that are used elsewhere - range, standard deviation, variance, mean deviation, coefficient of variation, median absolute deviation, interquartile range and quartile deviation.