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.
Standard Score. The standard score (more commonly referred to as a z-score) is a very useful statistic because it (a) allows us to calculate the probability of a score occurring within our normal distribution and (b) enables us to compare two scores that are from different normal distributions.he mean score is 60 out of 100 and the standard deviation (in other words, the variation in the scores) is 15 marks (see our statistical guides, Measures of Central Tendency and Standard Deviation, for more information about the mean and standard deviation).