Problem 7: The scores of students on the ACT
(American College Testing)
college entrance examination in a recent year had the normal
distribution with mean μ = 18
and standard deviation σ = 6. 100 students are randomly selected
from all who took the test.
a. What is the probability that the mean score for the
100 students is between 17
and 19 (including 17 and 19)?
b. A student is eligible for an honor program if his/her
score is higher than 25.
Find an approximation to the probability that at least 15 students
of the 100 students
are eligible for the honor program.
c. If the sample size is 4 (rather than 100), what is the
probability that more than
50% (not include 50%) students are eligible for the honor
program?
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