d.)Let X be a discrete random variable equal to the number of girls you have out of 6 children.
What is P(X=2 | X=1)
P(X=2∣X=1)?
a.) Assume that a website allows only lower case letters for password required to have a length of size 5, but does not allow the following choices for the password: (1) all 5 characters are identical and (2) any sequence ending with "gk". If a 5 letter sequence is randomly selected, what is the probability that it is a valid password?
(d) P(X=2 | X=1) = P(X = 2 X = 1) / P(X = 1)
Since X =2 and X = 1 cannot occur simultaneously, hence P(X = 2 X = 1) = 0
=> P(X=2 | X=1) = 0
(a)
Valid passwords = Total passwords - passwords with all identical characters - password ending with "gk"
Total passwords
5 characters each with 26 possible cases => (26)5
passwords with all identical characters
Choose any letter and make a password with all identical characters => 26
password ending with "gk"
Any character for first three positions and gk for last two positions
=> 26*26*26 = (26)3
Valid passwords = (26)5 - 26 - (26)3
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