8. Suppose that the IQ score for a person selected from a certain group of people
is approximately N(�; 100). Let X1;X2; : : : ;Xn be a random sample of such IQ
scores.
(a) How large should n be so that a 90% con�dence interval for � with maximum
error " = 1 is [ x 1:645(10)=
p
n ; x + 1:645(10)=
p
n ]?
(b) Verify your answer empirically. In particular, simulate 50 random samples
of size n from the normal distribution N(110; 100). Do approximately 90%
of these samples yield a con�dence interval that contains � = 110?
1 answer