Simple Random Sample.
Carlos Chacon


Definition of Simple Random Sample: is a sample design in which are drawn from a population in a way that gives every member and every combination of members an equal chance of being selected. The classic way of selecting a simple random sample is to assign every member of the population a number and then use a random number table to select the sample.

Simple Random Sample in my own words: is design a selection of member of the population in order to use the random number table of the sample.

Examples of the simple Random Sample:

An example of a simple random sample would be a group of 25 employees chosen out of a hat from a company of 250 employees. In this case, the population is all 250 employees, and the sample is random because each employee has an equal chance of being chosen.


stratifiedSample.gif


Step 1:
The first step is to find the total number of students (3475 above) and calculate the percent of students in each stratum.
    • School 1: 1050 / 3475 = .30
    • School 2: 565 / 3475 = .16
    • School 3: 1554 / 3475 = .45
    • School 4: 306 / 3475 = .09
Step 2:
Next, to select a sample in proportion to the size of each stratum (in this case school), the following number of students should be randomly selected:
    • School 1: 150 x .30 = 45
    • School 2: 150 x .16 = 24
    • School 3: 150 x .45 ~ 67
    • School 4: 150 x .09 ~ 14
This tells us that our sample of 150 students should be comprised of:
    • 45 students randomly selected from School 1
    • 24 students randomly selected from School 2
    • 67 students randomly selected from School 3
    • 14 students randomly selected from School 4