Question #65548

Seven terminals in an on-line system are attached to a communications line to the

central computer. Exactly four of these terminals are ready to transmit a

message. Assume that each terminal is equally likely to be in the ready state (i.e.

have a message to transmit). The central computer polls the terminals in a fixed

sequence without repetition. Let X be the # of terminals polled until the first

ready terminal is located (For example if the second terminal polled is ready,

then X=2, etc…)

a) Find the PMF (Probability Mass Function) of X

b) Find the mean and the Variance of X.

central computer. Exactly four of these terminals are ready to transmit a

message. Assume that each terminal is equally likely to be in the ready state (i.e.

have a message to transmit). The central computer polls the terminals in a fixed

sequence without repetition. Let X be the # of terminals polled until the first

ready terminal is located (For example if the second terminal polled is ready,

then X=2, etc…)

a) Find the PMF (Probability Mass Function) of X

b) Find the mean and the Variance of X.

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