Here Are The Shopping Times (in Minutes) For Each Of Fifteen Shoppers At A Local Shopping time in minutes 18 to 22 23 to 27 28 to 32 33 to 37

Frequency is the number of occurrences of a repeating event.
Here we have the events:
shopping time between occurences frequency
18 to 22: 20, 18 2
23 to 27: 27, 24, 26, 24, 24 5
28 to 32 29, 31 2
33 to 37 37, 34, 35, 33, 36, 32 6