EBP - Sampling

Question 1

What is a population?

Answer 1

Aggregate of objects, persons, or events that meet a specified set of criteria.

Question 2

Why is it important to be very specific when defining a population?

Answer 2

To develop inclusion/exclusion criteria.

Question 3

What is inclusion criteria?

Answer 3

Characteristics that have been shown to relate to the research issue & decide how important they are to your question.

Identifies appropriate subjects.

Question 4

What is exclusion criteria?

Answer 4

Factors that preclude someone from being a subject.

Question 5

What does inclusion and exclusion criteria determine?

Answer 5

They define the population.

Question 6

What is more important, how closely the sample represents the population, or how large the sample is?

Answer 6

Representation is more important.

Question 7

What is another name for a target population?

Answer 7

A reference population.

Question 8

What is the target/ reference population?

Answer 8

The researcher’s universe of interest.

Question 9

What is another name for the accessible population?

Answer 9

The experimental population.

Question 10

What is the accessible/ experimental population?

Answer 10

The available population.

Question 11

Can a sample be representative of the target population?

Answer 11

No, only the accessible population.

Question 12

When conducting a study on strength rehabilitation of the quads after THR surgery, what is the target population, and what is the accessible population?

Answer 12

Target –> Anyone with a total hip replacement

Accessible –> THR at one particular hospital, one physician, etc.

Question 13

Since samples are often a select subgroup of the population, how can the differences between this subgroup and the total population be accounted for?

Answer 13

Collecting data about non-participants.

Question 14

The hierachy for sample selection?

Answer 14

Target/ Reference Population –> Accessible Population –> Subject selection –> Non-Participants/ Participants –> Group Assignment –> Experimental Group/ Control Group

Question 15

What is a probability sample?

Answer 15

• Sample found through process of random selection
• Every unit in the population has an equal chance of being chosen
• With random sampling, sample considered to be representative of the population

Question 16

What are 5 examples of probability samples?

Answer 16

• Simple random
• Systematic
• Stratified random
• Disproportional
• Cluster

Question 17

What is a non-probability sample?

Answer 17

Samples determined using non-random methods.

Question 18

What are 4 examples of non-probability samples?

Answer 18

• Convenience
• Quota
• Purposive
• Snowball

Question 19

What is sampling error?

Answer 19

The difference between the population’s average, and the sample average.

Question 20

Why can sampling error not be calculated in non-random samples?

Answer 20

The probability of being selected is not known.

Question 21

What limits the generalizability of non-probability samples?

Answer 21

Being unable to to calculate the sampling error.

Question 22

For all methods of random sampling, what must the researcher have in their possession?

Answer 22

A list of the accessible population.

Question 23

What are some examples of simple random sampling?

Answer 23

• Rolling dice
• Drawing names from a hat
• Random numbers from a table

Question 24

How is a sampling interval calculated, and what type of sampling is it used in?

Answer 24

Total accessible population / sample size.

Used in systematic sampling.

Question 25

Is simple random sampling equal to systematic sampling?

Answer 25

Yes, as long as no pattern or order exists in the listing.

Question 26

What is stratified random sampling?

Answer 26

Dividing members into homogeneous, non-overlapping sets of strata by relevant characteristics.

Question 27

How can stratified random sampling reduce sampling error?

Answer 27

Increases representativeness of population.

Question 28

What is a proportional stratified sample?

Answer 28

Want to take representative proportion of elements effected by variable. (1st, 2nd, 3rd years)

Question 29

What is disproportional sampling?

Answer 29

If one group is very small, take a disproportionately large proportion of the smaller group, and then control for the misrepresentation by calculating proportional weights.

Question 30

How are assigned weights determined in disproportional sampling?

Answer 30

The inverse probability of each group is taken, and then each individual is multiplied by the assigned weight.

Question 31

When is cluster sampling used?

Answer 31

When a complete listing of a population can't be obtained.

Question 32

How is a cluster sample obtained?

Answer 32

Successive random sampling of a series of units in the population. Ex) 20 states --> random sample of 100 rehabs --> randomly select 5 PTs (For a sample of 500)

Question 33

What is an advantage, and a disadvantage of cluster sampling?

Answer 33

Advantage: Convenience and efficiency when dealing with a large population Disadvantage: Increased sampling error with every sample drawn.

Question 34

What is another name for convenience sampling?

Answer 34

Accidental sampling.

Question 35

What is convenience/ accidental sampling?

Answer 35

Subjects chosen on basis of availability.

Question 36

What is the major limitation of convenience sampling?

Answer 36

Potential bias of self-selection. Volunteers may be atypical of target population.

Question 37

What is consecutive sampling?

Answer 37

First come, first serve.

Question 38

What is quota sampling?

Answer 38

Guiding the sampling process so that an adequate number of subjects are obtained for each stratum so that the sample resembles the target population.

Question 39

What is a better sampling technique: convenience or quota?

Answer 39

Quota.

Question 40

What is purposive sampling?

Answer 40

Researcher handpicks subjects according to a set of defined characteristics.

Question 41

What is a limitation of purposive sampling?

Answer 41

Generalizations are limtetd to those who have these same characteristics.

Question 42

Is purposive sampling associated with qualitative or quantitative methodologies?

Answer 42

Qualitative.

Question 43

What type of sample is typically created by purposive sampling?

Answer 43

A homogenous sample.

Question 44

When is snowball sampling used?

Answer 44

When subjects with specific characteristics are hard to locate.

Question 45

What is snowball sampling?

Answer 45

Subjects are identified with specific characteristics. Subjects are then interviewed and asked to identify others they may know that are similar.

Question 46

Is snowball sampling associated with qualitative or quantitative methodologies?

Answer 46

Qualitative.

Question 47

Are probability or non-probability samples used more often in clinical research?

Answer 47

Non-probability due to difficulties in obtaining random access to populations.

Question 48

What judgement call must a researcher make to determine a non-probability sample's generalizability?

Answer 48

The researcher must determine if the characteristics of the sample are sufficiently different from those of the target population to limit generalizations.

Question 49

How can risks of interpretive error by researchers about generalizibility of a sample be reduced in non-probability sampling?

Answer 49

By replicating studies.