Question

Select one type of Probability sampling discussed in your textbook and provide an example of how you could use this sampling strategy to conduct a research study. What would be the strengths and weaknesses of your selected strategy in terms of external validity and sampling error?

Answer 1

Simple Random Sampling (SRS)-It is probability sampling.Simple Random sampling is used when whole population is accessible and the investigator have the list of all subjects in this target population. The list of all subjects in the population is called "sampling frame". From this list we draw a random sample using lottery method, Simple Random table or using computer generated Random Number.

We want to study the advantage of teaching method in college (Assuming there are 5000 students in college)

Step 1: Make a list of all the students in the college. (as mentioned above there are 5000 students in the college, the list must contain 5000 names).
Step 2: Assign a sequential number to each students (1,2,3…n). This is your sampling frame (the list from which you draw your simple random sample).
Step 3: Figure out what your sample size is going to be. (In this case, the sample size is 500).
Step 4: Use a random number generator to select the sample, using your sampling frame (population size) from Step 2 and your sample size from Step 3. For example, if your sample size is 500 and your population is 5000, generate 500 random numbers between 1 and 5000.

Strength of the study-

>A simple random sample is one of the methods researchers use to choose a sample from a larger population.
>Major advantages include its simplicity and lack of bias.

Weakness of this study - In simple random sampling an accurate statistical measure of large population can only be obtained when a full list of population in the study is available.In some instances, details on a population of students at a university or a group of employees at a specific company are accessible through the organization that connects each population.

External validity-Here the result of the college can not be generalizable to all other colleges because here we selected homogeneous population.(external bias) And also we can't generalize for all the other state students because we selected very few students on the basis of very few students we can't apply to other college.

When we increase the sample size the sample approaches to population and decreases the sampling error.

Population-The group of individual under study called population.In other words population is aggregate of objects animate or inanimate under study.The population may be finite or infinite.

Sample-A finite sub-set of population is called sample. Sample is almost representative of all the population. The total individual in the sample is called sample size.

Sample Error-The error involved in approximating population from sample characteristics. It is inherent and unavoidable in any sampling scheme.