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A physical therapist participates in a research study examining the optimal frequency for performing a lower extremity strengthening exercise. The therapist is worried the results of the study may not be generalizable since non-probability sampling was used. Which of the following is considered a type of non-probability sampling?

1. Snowball sampling
2. Simple random sampling
3. Systematic sampling
4. Cluster sampling

Transcript

Welcome back to the Scorebuilders’ Question and Answer Podcast! This podcast provides members of the Scorebuilders’ team with the opportunity to explore challenging multiple-choice examination questions with students actively preparing for the licensing examination. My name is Scott Giles and I will be your host for today’s journey.

Ready? Let’s go!

A physical therapist participates in a research study examining the optimal frequency for performing a lower extremity strengthening exercise. The therapist is worried the results of the study may not be generalizable since non-probability sampling was used. Which of the following is considered a type of non-probability sampling?

1. Snowball sampling
2. Simple random sampling
3. Systematic sampling
4. Cluster sampling

Let’s review both Probability and Non-Probability Sampling.

Probability Sampling
Probability sampling is a method of sampling that uses some form of random selection. Every member of the population must have the same probability of being selected for the sample since the sample should be free of bias and representative of the population.

Non-probability Sampling
Non-probability sampling is any method of sampling that does not involve random selection of subjects.

The question offers several specific pieces of extraneous information. However, to answer the question correctly, a student only needs to identify the non-probability sampling method.

Let’s dig in! 

Option 1 - Snowball sampling
Snowball sampling is a type of non-probability sampling in which subjects are identified by asking existing subjects to identify the names of other potential participants. 

Snowball sampling is used when the characteristic to be studied is rare and it would be extremely difficult and costly to identify individuals with this characteristic.

Option 2 - Simple random sampling 
Simple random sampling is a type of probability sampling in which subjects have an equal chance of being selected for the sample. The sampling method often relies on a table of random numbers or a random number generator on a computer to determine the sample. 

Simple random sampling is not the most statistically efficient method of sampling and may not result in a representative sample since it is the luck of the draw.

Option 3 - Systematic sampling 
Systematic sampling is a type of probability sampling in which subjects are selected by taking every nth subject from the population. The size of the interval is based on the size of the population and the desired sample size. 

The greatest advantage associated with this sampling technique is its simplicity.

Option 4 - Cluster sampling 
Cluster sampling is a type of probability sampling in which the population is divided into clusters or areas (usually along geographic boundaries) and a random sample of the clusters is selected. Then, all of the units in the selected samples are measured. 

The sampling technique is less costly and more efficient than simple random sampling, especially when the population is spread across a wide geographic region.

Option 1 is a form of non-probability sampling while options 2, 3, and 4 are forms of probability sampling.

This fact certainly expedited the decision making process!

The correct answer is Option 1

Let’s explore the all student data:
44% of students selected Option 1, Snowball sampling, the correct response
12% of students selected Option 2, Simple random sampling
17% of students selected Option 3, Systematic sampling
27% of students selected Option 4, Cluster sampling

System Classification
This question is a Non-Systems question which represents approximately 14% of all exam items.

Content Outline Classification
This question is a Safety and Protection; Professional Responsibilities; Research question which represents approximately 8% of all exam items.

Level Classification
This question is a Level 1 question since the question requires students to possess basic foundational academic knowledge. Remediation of Level 1 questions occurs through academic review of entry-level content using textbooks, review books, Basecamp, and flash cards.

Academic Focus Area
Looking to review related academic content? Check out page 834 in PTEXAM: The Complete Study Guide.

Thanks for joining us on the Scorebuilders Q and A podcast! See you next week!