'There's a huge misconception that if someone sneezes a lot then they must have hay fever,' says Dr Adrian Morris of the Surrey Allergy Clinic. From dogs to dust mites and pollen to latex, it's thought that 40 per cent of us suffer from an allergy.
The mean absolute deviation is the average of the positive distances of each point from the mean. The larger the MAD, the greater variability there is in the data (the data is more spread out). The MAD helps determine whether the set's mean is a useful indicator of the values within the set.
In fact, the mean absolute deviation from the median is always less than or equal to the mean absolute deviation from any other fixed number. The mean absolute deviation from the mean is less than or equal to the standard deviation; one way of proving this relies on Jensen's inequality.