2.5 Cumulative Frequency Graphs and Percentiles

Percentiles

• p^th found p-percent of the way through a set of ordered data; it is the value such that p percent of data fall at or below it

• location is found using (p/100)(n+1)^th

• 25^th percentile is p₂₅

• What percentile a data point is in is found with:

  • p=100*(L+0.5E)/n

  • L is the number of values below the data poin

  • E is the number of values equal to the data point

  • n: total # of values

In Grouped Data…

Value of Quantile is taken to be the midpoint of that interval

if the interval is at the boundary of 2 intervals, take that boundary as its value

Cumulative Frequency Graphs

depict a running total of frequency dat

• Make it easer to find proportions of data which helps with percentiles