The average number absences in a large school is 85 students per day with a standard...
The average number absences in a large school is 85 students per day with a standard deviation of 37. In a SRS of 30 days what is the probability that the mean number of absences is between 75 and 95?
0.14 0.22 0.86 0.99
Homework Answers
Sol:
mean=85
sd=37
sample size=n=30
sample sd=s=sigma/sqrt(n)=37/sqrt(30)=6.755245
sample follows normal distribution as n>=30
P(75<X<95)
P(75-85/6.755245<Z<95-85/6.755245)
P(-1.4803<Z<1.4803)
P(Z<1.4803)-P(Z<-1.4803)
0.9306-0.0694
0.8612
ANSWER:
0.86
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