Homework Help: statistics

Posted by Anonymous on Sunday, July 22, 2012 at 11:39pm.

) 43% of adults receive phone calls during the day. Amongst 10 randomly
selected people find the probability that
a. Adults receive exactly 4 phone calls.
b. Adults receive 8 or more phone calls.

statistics - MathMate, Monday, July 23, 2012 at 9:19am
Binomial distribution:
p=0.43 (probability of success)
q=1-p=0.57
N=10 (sample size)

Probability of r successes out of N:
P(X=r)=C(N,r)p^r*q^(N-r)
and C=combination=N!/(r!(N-r)!)
a. r=4
P(X=4)=C(10,4)*0.43^4*0.57^(10-4)=0.24

b. r≥8
P(X≥8)
=P(X=8)+P(X=9)+P(x=10)
= similar calculations as above

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