Independent trials that result in a success with probability p are successively performed until a total of r successes is obtained. Let X= # of trials that are needed (total number, including the r successes).

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Independent trials that result in a success with probability p are successively performed until a total of r successes is obtained.
Let X= # of trials that are needed (total number, including the r successes).
In the following questions please mark the correct answer. Use q=1-p.
Find E(X).
Hint:
You might find it useful to use a geometric series with 0 <*< 1,
s =E" = (1– m) ',
and the order k derivative
Cn (n – 1).. (n – k + 1) ="-* = k!/(1 – #)**.
1/p
np
np
r/p
O (n – 1)p
none of these
Transcribed Image Text:Independent trials that result in a success with probability p are successively performed until a total of r successes is obtained. Let X= # of trials that are needed (total number, including the r successes). In the following questions please mark the correct answer. Use q=1-p. Find E(X). Hint: You might find it useful to use a geometric series with 0 <*< 1, s =E" = (1– m) ', and the order k derivative Cn (n – 1).. (n – k + 1) ="-* = k!/(1 – #)**. 1/p np np r/p O (n – 1)p none of these
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