Question

X is a binomial variable with n = 20. What is the mean of x if it is known that x is symmetric

Answer 1

x is bernoulis variable

Answer 2

Mean = n x p = 20 x 0.5 = 10 (In the shape of x is symmetry and for symmetric binomial distribution value of p is always 0.5)

Binomial distribution occurs where there are two possible outcomes where one is success and other one is failure. For example if we flip a coin there are two possibilities it can be either heads or it can be tail. Chances here are 50:50 so the p value is always 0.5 in this case.