Check answer a) for the (1-P) to the power of x-r it's not five since x is five. It should be (5 - 2) = 3 . According to the formula. Unless there's another reason that wasn't correctly explained.
it's correct, you have to understand this beyond looking at just formulas. You are talking about the trial version which has X as the total trials ,r # of successes and x-r on (1-p) as failures in X.
Ya total trials is 7 but he is lost. He probably doesn’t understand with its 6 choose 1, which are trials before the rth success choose r-1 successes. But he is confused again on p^r.
You don’t understand or maybe you do now. This is not binomial distribution. It looks funny but you really have to understand and forget about formulas. The question said EXACTLY 5 fails calls, before the second success. You are thinking about 5 trials. Exactly 5 failed means (1-p)^5. It’s (X+r-1 r-1)p^(r-1)*(q)^x then times the rth success which is p. Don’t memorize, understand why.
it seems in comment section, many people still doesn't understand negative binomial
are you sure that you correctly plugged in the formula?
Check answer a) for the (1-P) to the power of x-r it's not five since x is five. It should be (5 - 2) = 3 . According to the formula. Unless there's another reason that wasn't correctly explained.
it's correct, you have to understand this beyond looking at just formulas. You are talking about the trial version which has X as the total trials ,r # of successes and x-r on (1-p) as failures in X.
it says 5 failed calls *before his second success.* This is 7 total trials. Answer is correct
Ya total trials is 7 but he is lost. He probably doesn’t understand with its 6 choose 1, which are trials before the rth success choose r-1 successes. But he is confused again on p^r.
You made learn
There is a mistake here: (x = n -r ) that is the number of trails minus the number of successful outcome.
You don’t understand or maybe you do now. This is not binomial distribution. It looks funny but you really have to understand and forget about formulas. The question said EXACTLY 5 fails calls, before the second success. You are thinking about 5 trials. Exactly 5 failed means (1-p)^5. It’s (X+r-1 r-1)p^(r-1)*(q)^x then times the rth success which is p. Don’t memorize, understand why.
boooooooooooo!!!!
Your formula is wrong