As only 3 students came to attend the class today, find the probability of exactly 4 students to attend the class tomorrow

Answer 1

The variable X is the number of students who attend the class. Then x=3 is the number of students who attend the class today.

This is a binomial variable with the probability that a student attends the class p=0.5 and n= number of students in the class. This value is missing.

P(X=4)=?

Assume you know the value of n. Then P(X=4)=nC4 (0.5)⁴(0.5)^n-4