Question

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Answer 1

Answer:

Step-by-step explanation:

Given that  a school has 20 classes: 16 with 25 students in each, three with 100 students in each, and one with 300 students for a total of 1000 students.

a) Y = no of students in the class out of 20 selected at random

Y can take values as

Y          25     100    300   Total

freq      16        3          1       20

P(Y)     16/20   3/20   1/20     1

y*p      20        15       15       50

E(Y) = 50

b) X = size of student from which one student is taken at random

X                                    25       100    300     Total

No of classes                16           3         1         20

Total students          

(X*no of classes)           400    300    300     1000

P(x)                                 0.4      0.3       0.3          1

X*P                                 160       90      90       240

E(x) =240

c)   On an average,   a student at this school is in a class with 240 students. On average, a class at this school has 50 students.

i.e. expectation of number of students in a class is 50 while expectation of a student having students in the class is 240