With penalties and minimum withdrawal requirements to consider, timing is of the utmost importance when taking money from your IRA. (Getty Images) Individual retirement accounts, commonly known as IRAs, are retirement fund staples for many people.
In statistics, the mean is the mathematical average of a set of numbers. The average is calculated by adding up two or more scores and dividing the total by the number of scores. Consider the following number set: 2, 4, 6, 9, 12. The average is calculated in the following manner: 2 + 4 + 6 + 9 + 12 = 33 / 5 = 6.6.
Z-scores (standard scores) raw scores stated in standard deviation terms. a measure of how many standard deviations a given raw score is from the mean. A negative number (e.g. -1) means the score falls below the mean. 0 = the mean. shape of the distribution does not change when scores changed to z-scores (linear transformation)