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Consider a population of 6 students. Suppose we know the test scores of the students to be
a. Find the mean U and variance S2 of the population.
b. How many SRS’s of size 4 are possible?
c. List the possible SRS’s. For each, find the sample mean. Using Equation (2.9), find V ().
d. Now let stratum 1 consist of students 1–3, and stratum 2 consist of students 4–6.
How many stratified random samples of size 4 are possible in which 2 students are selected from each stratum?
e. List the possible stratified random samples. Which of the samples from (c) cannot occur with the stratified design?
f. Find str for each possible stratified random sample. Find V (str), and compare it to V (). |
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