chapter 006 revised fall2015

Copyright © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins

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)

Copyright © 2015 Wolters Kluwer • All Rights Reserved

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.

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.

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

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.

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.

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.

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?

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.

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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