Answer:
19.5
Step-by-step explanation:
To find the interquartile range, we need to find the first and third quartile of the data.
So, first, we need to find the median. The median is the number that divides the organized data into two equal parts.
61, 65, 65, 66, 72, 75, 77, 79, 81, 89, 92, 99
In this case, the numbers that divide the data into two equal parts are 75 and 77, so the median is
median = (75 + 77)/2 = 76
Now, the first quartile will be the median of the first half of the data, so
61, 65, 65, 66, 72, 75
First quartile = (65 + 66)/2 = 65.5
Because 65 and 66 divide the first half of the data into two equal parts.
In the same way, the third quartile is equal to:
77, 79, 81, 89, 92, 99
Third quartile = (81 + 89)/2 = 85
Therefore, the interquartile range is
Interquartile range = Third quartile - First quartile
Interquartile range = 85 - 65.5
Interquartile range = 19.5
So, the answer is 19.5