When calculating percentiles, ie the 33rd percentile, do you use the lower limit of the group that contains the 33rd

Question

percentile? as in this case:
70-79 11 46 80.7
60-69 9 35 61.4
50-59 8 26 45.61
40-49 7 18 31.58
Would you use the number 49.5??

Answer 1

Thank you for using the Jiskha Homework Help Forum. If I understand your question the 1/3 (by the rule of math) would be the lower percentile. 2/3 would be higher. The demarcation is the 1/2.

Answer 2

It might be better if you interpolated within the interval to get the 33rd percentile more exactly.

For example, if 70 was the 30th percentile and 79 was the 40th, then 73 would be the 33rd percentile.

I hope this helps a little more. Thanks for asking.