In: Statistics and Probability
A quiz is created by choosing for each question on the quiz one
possible version at random from a bank of
possible versions of the question. There are 20 versions in the
bank for each question.
A specific question on the quiz involves a one-sample test for the
population mean with hypotheses
H0 : µ = 15
Ha : µ > 15
with all versions of the question involving a sample of size n =
35.
Seven versions of the question give the population standard
deviation as σ = 3. Six versions give the sample standard
deviation as s = 4 . 2. The remaining versions give the sample
standard deviation as s = 5 . 7.
Let c∗ be the critical value for the rejection region on this
question. Calculate E [ c∗ ].
ANSWER::
We assume that the significance level to be 0.05.
Critical value of z for 0.05 significance level is -1.645
Degree of freedom = n-1 = 35-1 = 34
Critical value of t for 0.05 significance leve and df = 34 is -1.691
For = 3
Standard error = 3 / = 0.5070926
Since we know the population standard deviation, we will use z score to estimate the critical value.
c* = 15 - 1.645 * 0.5070926
= 14.16583
For s = 4.2
Standard error = 4.2 / = 0.7099296
Since we do not know the population standard deviation, we will use t statistic to estimate the critical value.
c* = 15 - 1.691 * 0.7099296 = 13.79951
For s = 4.2
Standard error = 5.7 / = 0.9634759
Since we do not know the population standard deviation, we will use t statistic to estimate the critical value.
c* = 15 - 1.691 * 0.9634759 = 13.37076
The PMF of C* is,
P(c* = 14.16583) = 7/20
P(c* = 13.79951) = 6/20
P(c* = 13.37076) = 1 - 7/20 - 6/20 = 7/20
E[c*] = (7/20) * 14.16583 + (6/20) * 13.79951 + (7/20) * 13.37076
= 13.77766
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