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From: "http://www.cooltime.com/" <[log in to unmask]>
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To: "Parkinson's Information Exchange" <[log in to unmask]>
Subject: Mean, Median, Mode: Different forms of average
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OK, let's get some statistics-101 here. Average is an imprecise term.
There are three commonly used measures of "Average" ... these are the
mean, median and the mode.
1. Mean: This is the arithematic mean and is what most people think of
when you say "average." The mean equals (the sum where i ranges from 1 to
n of data items X sub i)all divided by N (in other words, add up the ages
and divide by the number of PWPs).
2. Median: This is the value of the data point that lies in the center
of an ordered distribution. Example: line up PWPs age of onset from
lowest to highest...the person in the middle is the median observation:
22, 28, 31, 43, 57, 61, 62, 63, 82
The median helps trim out the influence of "outliers" or extreme values in
a data set.
3. Mode: The mode is simply the number oserved most frequently (it
appears the most times in the data set.) Ex:
22, 28, 43, 57, 60, 60, 62, 63, 63, 77, 77, 77
The mode in this case is 77. Note that all three sets of data points I
have shown here have to low of an "N" to mean anything at all (not enough
people to get a meaningful average from.)
All three of these are "averages" but if I had to give an opinion, I would
choose the median to represent the "average" age of onset in this case
since the distribution is skewed and truncated on both ends.
---
All You Touch And All You See [log in to unmask] ____
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