The marks obtained by 40 class X students in a math paper of 50 marks, are presented in the table. Find the mean using direct method.
Marks obtainedNumber of students0−10310−20420−301330−401540−505
Class mark for a class interval
=upper class limit+lower class limit2
e.g: for the first class interval of 0-10
= 0+102
= 5
Similarly the class mark for each class interval can be found. Look at the table.
Class intervalNumber of students(fi)Class mark(xi)fixi0−10351510−204156020−30132532530−40153552540−50545225Total∑fi=40∑fixi=1150
Mean=∑fixi∑fi=115040=28.75