Chapter 006 Revised Fall2015

N307 Research for Evidence-Based Practice

SDSU IV CampusFall 2015

N307 Research for Evidence-Based Practice

SDSU IV CampusFall 2015

Chapter 6: SamplesTo What Types of Patients Do These Research Conclusions Apply—Who Was in the Study?

(Used with modification by L. Greiner Fall 2015)

Key TermsKey Terms

• Population• Sample• Non-probability sample• Probability sample• Recruitment• Inclusion criteria• Bias

The differences between the terms “sample” and “population” are best described in this way

The differences between the terms “sample” and “population” are best described in this wayA. There is really no difference

B. A sample is a subset of a population

C. A population is the ideal sample

D. None of the above

E. All of the above

Important DistinctionsImportant Distinctions

• Population– All the people who have the condition or

characteristic of interest– May also be called “population of interest”– May also be called “target population”

• Sample– A subset of the population– Does the sample reflect the population?

Quantitative sampling strategies aim for subjects who match the population of interest.

A. True

B. False

C. It depends

Quantitative studies that seek to predict use sampling strategies to reduce extraneous factors.

A. True

B. False

C. It depends

Important Questions to AnswerImportant Questions to Answer

• To what types of patients do these research conclusions apply?

• Three questions

Example of Study Sample Criteria for ParticipationExample of Study Sample Criteria for Participation

The population for the CVD risk factors in diabetes study were:

• Children with insulin-dependent diabetes

• Children without ketosis

• Children without other chronic conditions

• Children without known lipid abnormality

• Children between ages 1 and 8 years

Sampling strategies in quantitative studies are used to avoid “bias”. Bias in this case refers to

A. When the researcher believes he/she knows the answer in advance of the study

B. When random sampling is best but not selected

C. When some factor changes the results leading to incorrect conclusions

Probability sampling uses strategies to ensure everyone has an equal chance of participating.

A. True

B. False

C. It depends

Table of Random NumbersTable of Random Numbers

Probability sampling strategies include which of the following?Probability sampling strategies include which of the following?A. Simple random

B. Stratified random

C. Systematic

E. All of the above

Nonprobability sampling should not be used in quantitative studies.

A. True

B. False

C. It depends

Nonprobability sampling strategies include which of the following?

Nonprobability sampling strategies include which of the following?A. Convenience

B. Quota

C. Purposive

E. All of the above

Nonprobablity sample sizes are usually smaller than probability sample sizes.

A. True

B. False

C. It depends

Older, lonely people are more likely to volunteer to be in a study. This is an example of which type of sampling problem?

A. Response rate

B. Bias in subject recruitment

C. Incomplete data

D. None of these

E. All of these

Qualitative sampling strategies aim for subjects who match the population of interest.

A. True

B. False

C. It depends

In qualitative research, which of the following sampling strategies is used?

In qualitative research, which of the following sampling strategies is used?A. Convenience

B. Snowball

C. Purposive

E. All of the above

Does the Sample in the Study Fit With the Population of Interest?

Differences in Sampling ApproachesDifferences in Sampling Approaches

Qualitative

• Goal is to include as many sources as possible to add richness and depth

• Approach is driven by data collection and evolves.

• Members of sample called participants

Quantitative

• Goal is to limit effects of outside variables (bias), to control variation

• Approach is established at the beginning of study.

• Members of sample called subjects

Qualitative Sampling ApproachesQualitative Sampling Approaches

• Convenience

• Snowball

• Purposive

QUESTIONQUESTION

Is the following statement True or False?

A purposive sample consists of members of the population who are readily available.

ANSWERANSWER

False.

A convenience sample consists of members of the population who are readily available. A purposive sample consists of participants who are intentionally or purposefully selected because they have certain characteristics related to the purpose of the research.

Quantitative Sampling ApproachesQuantitative Sampling Approaches

• General approaches

1. Nonprobability sample

2. Probability sample

Nonprobability SamplesNonprobability Samples

• Convenience sample

• Sampling frame

• Quota sample

• Matched sample

Nonprobability Samples (cont.)Nonprobability Samples (cont.)

• Strengths

• Weaknesses

QUESTIONQUESTION

A sample that is selected with a goal of having an established number of subjects who represent one or more important characteristics is a ___________.

A.matched sample

B.quota sample

C.random sample

D.snowball sample

ANSWERANSWER

B. quota sample

A sample that is selected on the basis of a goal of having an established number of subjects who represent one or more important characteristics recommendations based on results is a quota sample. The quota has been filled with desired participants.

Probability SampleProbability Sample

• Random sample

• Random selection

• Stratified random sample

• Cluster sampling

• Systematic sampling

Summary of Sampling StrategiesSummary of Sampling Strategies

Probability SamplesProbability Samples

• Strengths

• Weaknesses

QUESTIONQUESTION

A process of sampling in stages starting with groups within the population and then individuals within the groups is a ____________.

A.cluster sample

B.random sample

C.stratified random sample

D.systematic sample

ANSWERANSWER

A. cluster sample

A process of sampling in stages starting with groups within the population and then individuals within the groups is a cluster sample. Small clusters form and then participants are selected from within.

Sample SizeSample Size

• Qualitative

– Data saturation

• Quantitative studies

– Power analysis

In SummaryIn Summary

• Sample versus population

• Goals and approaches differ

• Sampling affects the results and conclusions of the study

• Sampling answers “the” question

Questions?Questions?

Chapter 006 Revised Fall2015

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