20 , 23 , 28 , 14 , 13 , 24 , 18 , 11

There are 8 observations, so the median is the mean of the two middle numbers of the arranged set of data. Splitting the observations either side of the median gives two groups of observations. The median of the lower half of data is the lower or first quartile. The median of the upper half of data is the upper or third quartile.

The median of the lower half of data is the lower or first quartile

The median of the upper half of data is the upper or third quartile

Arrange the terms in ascending order.

11,13,14,18,20,23,24,28

The median is the middle term in the arranged data set. In the case of an even number of terms, the median is the average of the two middle terms.

18+202

Remove parentheses.

18+202

Cancel the common factor of 18+20 and 2.

Factor 2 out of 18.

2⋅9+202

Factor 2 out of 20.

2⋅9+2⋅102

Factor 2 out of 2⋅9+2⋅10.

2⋅(9+10)2

Cancel the common factors.

Factor 2 out of 2.

2⋅(9+10)2(1)

Cancel the common factor.

2⋅(9+10)2⋅1

Rewrite the expression.

9+101

Divide 9+10 by 1.

9+10

9+10

9+10

Add 9 and 10.

19

Convert the median 19 to decimal.

19

19

The upper half of data is the set above the median.

20,23,24,28

The median is the middle term in the arranged data set. In the case of an even number of terms, the median is the average of the two middle terms.

23+242

Remove parentheses.

23+242

Add 23 and 24.

472

Convert the median 472 to decimal.

23.5

23.5

Find the Upper or Third Quartile 20 , 23 , 28 , 14 , 13 , 24 , 18 , 11