In: Math
Let xi, i = 1,2,...,n be independent realizations from a population distributed like a Pareto with unknown mean.
(a) Compute the Standard Error of the sample mean. [Note:
By“compute”, I mean “find the formula for”]. What is the
probability that the sample mean is two standard deviations larger
than the popula-
tion mean?
(b) Suppose the sample mean is 1 and the Standard Error is 2. Con- sider a test of the hypothesis that the population mean is 0, against the alternative that it is greater. What is the p−value? Compute a 5% confidence interval [Note: Use the Normal as an approx- imation for simplicity]. What is the type II error if the actual population mean is 2?
a) Let and be population mean and population standard deviation respectively.
Let = sample mean.
Standard error of sample mean is
Required Probability
By using Chebychev's inequality
( If X is a random variable with mean and Variance then for any positive integer k
)
Hence required probability is
Probability that sample mean is two standard deviation larger than population mean is atmost 0.25.
b ) From the information
We have to testing the hypothesis
against
The value of test statistic is
Under Ho the value of test statistic is
Since the test is right-tailed p-value is obtained by
from normal probability table
P ( Z > 0.50) = 0.3085
p-value = 0.3085.
5% confidence interval for population mean is
Alpha : level of significance = 0.95
From normal probability table
= (0.8746, 1.1254)
Since the test is right-tailed At 5% level of significance the critical region is Z > Zalpha/2
i.e.
Under Ho
Hence Critical region is and accepance region is
Probability of Type II error = P ( Accept Ho / Ha is true)
= P ( Z < 0.64)
From normal probability table
P ( Z < 0.64) = 0.7389 = P ( Type II error).