Answer:
Follow the instruction, do the rest
Step-by-step explanation:
Class Mark - an average of two numbers in class: [(17+20)/2] = 18.5
Lower Boundary - lower of two numbers minus 0.5: 17-05 = 16.5
Upper Boundary - higher of two numbers plus 0.5 = 20 + 0.5 = 20.5
CF less than (<) - frequency + all frequency below the class = In class (1 to 4) the cf < is 1 while in class (5 to 8), the cf < is 3.
CF more than (>) - frequency + all frequency above class = In class (17 to 20) the cf > is 10 while class (13-16) the cf > is 26
