Question

You wish to determine the GPA of students at your school. Describe what process you would go thru to collect a sample if you use a stratified sample.

Answer 1

Objective: To determine the GPA of students at our school

Step 1:

Let

N = Total number of students at our school

Obtain the value of n = Sample Size to be selected from the population applying statistical techniques.

Step 2:

Divide the entire school into a number of k homogeneous non-overlapping independent groups, called strata, containing N₁, N₂, ..., N_k students so that N₁ + N₂ + ...,+ N_k = N

Step 3:

Apportion the Sample Size = n to each of the k strata proportionally as n₁, n₂, ..., n_k students so that n₁ + n₂ + ...,+ n_k = n.

Step 4:

Through Simple Random Sample (SRS) technique, from Stratum 1, select n₁ students from N₁ students.

from Stratum 2, select n₂ students from N₂ students

etc.

from Stratum k, select n_k students from N_k students

Step 5:

Thus, we will have n students from N students.

This will enable us to determine the GPA of students at our school employing Stratified Sampling.