Mean 86.5 ((70,70,75,85,90,90,90,90,100,105 )/ 10 )
Median:90 (90+90 /2 = 90)
Mode: 90 (The number that comes up the most)
To find the quartiles just divide the data set in fours so that each set has three numbers.
Upper Quartile: 90
Lower Quartile: 75
