For example, consider this set of temperature readings taken once a day at the same time every day for 10 days: 15, 15, 16, 16.5, 15, 15.5, 25, 16, 15, 16 (degrees Centigrade). A simple average of the entire set of readings is 16.5 degrees. That’s a straightforward mathematical perspective taken without questioning the validity of any of the readings. But considering them more closely, wouldn’t it seem odd that when all the readings hover around the 15 or 16 degree mark, there’s one reading of 25 degrees? There’s no gradual increase of temperature to 25 in the preceding days, followed by a gradual decrease back to the 15 degree mark in the succeeding days. It’s a sudden spike. Do things like that usually happen? Maybe certain freak weather conditions could cause such an oddity, but how likely could that be? If we exclude that particular reading from our calculation, the average changes to 15.55 degrees, which is almost a whole degree lower.