15 XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX18 XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX XXXXXXXXXX Let say above “normal distribution” is the average test of statistic, there only have 1 students score 10 and...

                             15

                       14 15 16

                  13 14 15 16 17

            12 13 14 15 16 17 18

      11 12 13 14 15 16 17 18 19

10 11 12 13 14 15 16 17 18 19 20

Let say above “normal distribution” is the average test of statistic, there only have 1 students score 10 and 20. 15 is  mode, mean and median of the whole class score. There are 6 student score 15.

My teacher say it is not a normal distribution.

Could someone explain to me why it is not a normal distribution?