What is Central tendecy?

There are three statistical measures of "central tendency" - mean, median and mode. Combined, they give a picture of how close the data values cluster around a single "average" value. Normally, when someone talks of AVERAGE they are talking about the MEAN - where you add all the values and divide by the number of data points. But that value can be greatly affected by extreme values (e.g., the Mean of the following numbers: 3, 4, 4, 5, 4, 3, 27, 4, and 4 would be skewed by that one value that is not close to most of the others). The MODE of the numbers I gave, however, is the value that occurs most frequently - 4. The MEDIAN, the point where half the values are higher and half are lower, would also be 4. So, you see, the Central Tendency would be toward the value 4 and there is a strong Central tendency in this set of values. You could have a different set of numbers (e.g., 3, 27, 118, 11, 2, 963, 48) and while you could calculate an arithmetic mean, you could see that it wouldn't be too useful since there is no real Central Tendency of the data.