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Understanding the science of statistics begins with the ability to interpret sets or series of data. In the case of purely numerical data, this in turn begins with an understanding of the three Ms of statistics: mean, median and mode.

Mean is another word for average. To find it, add the value of all given numbers in the set and divide the result by the number of entries. Even if all entries are whole numbers, the result will not always be as such. Take, for instance, the following set: 3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7 and 9. The sum of these numbers is 77, and there are 15 entries. Therefore, the average is 5.1333 or 5 2/15, even though all of them are whole numbers. When finding mean, the order of the entries is inconsequential. This set could be kept as is, or it could be rearranged in ascending order to appear as 1, 1, 2, 3, 3, 4, 5, 5, 5, 6, 7, 8, 9, 9 and 9 and the result would still be the same.

For long lists with consistent intervals, there is a fast way to find the mean without using a calculator. Take, for instance, all integers from 1 through 100. Add the lowest and highest numbers, and we get 101. Mark those off and move inward, and we have 2 + 99 = 101. Do it once more and we have 3 + 98 = 101. With the pattern made clear, we simply count how many permutations occur before we reach the middle. There are 50, going from 1 + 100 to 50 + 51.Multiply the number of permutations, 50, by the consistent result of each, 101 and get 5050. Divide by 100, and we get 50.5.

Order is essential, however, in finding the median. The median is the middle entry on the list. This is easy to remember if you recall that the wall dividing the two sides of the interstate, putting it right in the center, is also called a median. Anyway, in the case of a list of whole numbers with consistent intervals (such as 1, 2, 3, 4 or 12, 18, 24, 30) the median will always be a whole number if the number of entries is odd. If the number of entries is even, the median will only be a whole number if the interval is an even number.

This is because there can only be one median. Thus, if our marking off entries two at a time, one from each end of the list, results in two remaining entries at the middle, we must take the average of those two. This occasion will arise only in the instance of an even number of entries. If we have a consistently even interval, the average of those two will always be a whole number. This is because an even interval means that either both numbers

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