Example: Below is a table of 16 quiz scores ordered (and indexed) from least to greatest.

index 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

score 15 24 27 31 36 37 37 38 40 41 42 43 44 45 48 50

(a) Calculate P20

Answer: The index is given by i = 20/100 16 = 3.2. Since this is not a whole number we round up

toget i=4 and P20 =31.

(b) Calculate P25

Answer: The index is given by i = 25 /100 16 = 4, and we must average the 4th and 5th values to

get P25 = 33.5.

(c) Your Turn: Calculate P75 ?

(d) Your Turn: Calculate P90 ?