Bernulli to Binomial

[mkheidzedavid]

Hello!

I need some help. As we know binomial distribution is nothing more than several times repeated bernulli random experiment. Bernulli random experiment has 2 outcomes: 0 and 1. So X = 0; 1. In case of Binomial model we have several Xs. Xi = X1 + X2 + ... +Xn. And its expectation and variance are computed by decomposing that total X into n Xs. X = X1 + X2 + ... +Xn and then finding its mean and variance. Where Xs are uncorrelated. What I dont understand is the meaning of total X. Does it represent the total number of successes? Or total number of outcomes?

Thank you

 

[tylor]

i personally was taught that X is your total number of successes, and n was your total number of trials. and your probability was of course X/n

 

[amir]

as tylor said, X is total number of successes/failures, and n is total number of trials. So, you may repeat an experiment 10 (n) times but get 8 (X) of what you want, that is, 2 of your trails failed.
you can also define X as failures...