Average – Is That What You Want?

Statistics.  Did you just shudder when I said that word?  People are very dipolar about taking statistics classes.  Either they loved it or hated it.  Most are in the second group.  I think it is because they are so darn counterintuitive.  Which is why it is easy to use them to back up any point you want to make.

A friend of mine gave me a great book, named How To Lie With Statistics by Darrell Huff.  It was published in the 1954, so the numbers are a little dated, but the lessons are great.  It is a quick read and allows you to pick up on numbers that don’t quite look right.

Take the average, for instance.  I can tell you that the average high temperature in April in Portland, Maine is 53 degrees.  That says nothing about the daily fluctuations.  The record high was 89 degrees.  The record low was 8 degrees.  That is a lot of variability to be ready for, 81 degrees.  San Diego, California, on the other hand, has an average high of 61 in April, with record high and low of 98 and 41, respectively, only 57 degrees apart.  If you want a guarantee of a frost free April, go to San Diego.  But the average does not tell you that.

Another way to render an average meaningless is to conveniently not specify the data you used to calculate it.  Today, on areavibes.com, the median cost of a house in Portland, Maine is listed as $236,000.  At Zillow.com, the median cost is listed as $379,450.  That is a big difference!  It might meant the difference between you thinking it was reasonable to move there or not.  The difference probably comes from the area each is calling “Portland, Maine”.

So, when you look at an average, make sure you dig a little deeper.

Next post, I will talk about the different types of averages and how to interpret them.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s