A median and an average are two statistical methods of calculating the “middle” of a series of numbers.
A median price is simply the price that lies directly in the middle of a series of prices when arranged from lowest to highest, having an equal number of entries on either side. If there is an even number of entries, then the median is calculated as the average between the two entries closest to the middle.
Ex: Consider Series 1 ($125,000, $250,000, $265,000, $283,000, $327,000). The median price is $265,000, because it lies directly in the middle and has an equal number of prices (2) on either side.
If the series is expanded to include one more price at the end, so that we have Series 2 ($125,000, $250,000, $265,000, $283,000, $327,000, $512,000), the median price is now $274,000. This is equal to the average of the two numbers closest to the middle [($265,000+$283,000)/2=$274,000], since there is no single price that lies directly in the middle of the series with an equal number of prices on either side.
An average price is calculated by adding a series of prices together and then dividing this total by the number of prices that have been summed. Please note that this calculation cannot be performed using a group of median or average prices to find another average or median price (i.e. cannot use the “average of averages” or “median of medians” as a statistically relevant figure).
In Series 1 ($125,000, $250,000, $265,000, $283,000, $327,000) the average price is $250,000 [$125,000+$250,000+$265,000+$283,000+$327,000=$1,250,000; $1,250,000/5=$250,000).
If we use Series 2, the average price becomes $293,667 (rounded to the nearest dollar).