Median

The median is the middle data value when the data set is arranged in some order.  In the example shown below, colors are arranged in alphabetical order. In this case, green is the median of the set of colors.

Black  Blue  Green  Pink  Red

Now look at the data set we use in the last lesson.  Observe how the median is found.
 

[N2O] 0.05 m above surface
(nL / L)
325
307
309
316
321
312

Step 1: Order the data values in order of least to greatest.

307,  309,  312,  316,  321,  325

Step 2: If the n = an odd number, then the median is the middle data value of your set.  If n = an even number, go to Step 3.

Step 3: Find the two data values in the middle of your set.  In this case the numbers are 312 and 316.  Now, the median is equal to the average of these two numbers (their mean).  The median for this example is (312 + 316 ) / 2 = 314.

Quick Quiz: Find the median for the following data set:

pH Values
5.20
4.56
6.30
7.00
5.25

5.20
4.56
6.30
5.25

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