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Nursing Research. PART I. Lecture №17. Is nursing a profession? Q.#1: What are the criteria for a profession?. Nursing: Profession or Technical Occupation?. Pavalko’s (1971) Continuum Model for a Profession Theory Relevance to social values Education Motivation Autonomy

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Nursing research

Nursing Research


Lecture №17

Nursing research

Is nursing a profession?

Q.#1: What are the criteria for a profession?

Nursing profession or technical occupation

Nursing: Profession or Technical Occupation?

Pavalko’s (1971) Continuum Model for a



Relevance to social values





Sense of community

Code of ethics

Explore the meaning of a professional vs technical practice

Explore the Meaning of a Professional vs. Technical Practice

  • Describe the similarities or differences between the chef at the Brown Palace & the cook at the Village Inn?



Professional vs technical for all practice areas

Professional Practices

Have a culture that supports professional activities: frameworks, CE, research

Has a defined body of knowledge gained by formal education

Is a discipline with peer review and a code of ethics

Autonomy in practice with legislative and legal sanctions

Is an organized system of practice recognized by society

Technical Occupations

Are more likely to have more OJT than formal education.

Are skill focused

Have trade journals or technique trainings

Do not focus on what advances the practice

Develop through certifications

Want less accountability

Professional vs. Technicalfor all practice areas

Professional vs technical thinking and valuing

Professional thinking

More is best

Specialization in depth and breadth

Evidence-based education

Invests energy beyond the work-associations, research, reading

Expects self accountability

Resilient with change and believes change is valuable

Technical Thinking

Least is best

Specialization in depth

Experience is the primary educator

Conserves energy beyond the workday

Prefers others be accountable

Enjoys consistency and believes change is disruptive

Professional vs. TechnicalThinking and Valuing

Nursing research

Is research important to the profession?

Yes!! Research is important for

building a unique, systematic

body of knowledge about

a discipline

Nursing needs a systematic body of knowledge to

Nursing needs a systematic body of knowledge to ...

Promote Evidence-based practice

Give credibility to profession

Provide accountability for practice

Help document the cost-effectiveness of care (Nieswiadomy, 2008)

What is evidence based nursing practice

What is Evidence Based Nursing Practice?

  • Knowledge from science & research

  • Knowledge from experts

  • Knowledge from patients

  • Knowledge arriving in many forms

  • Has levels of power and rigor


Evidence based practice definition

Evidence Based Practice: Definition

  • “…the integration of current bestevidence with clinical expertise and patient values” (Sackett et al., 2000)

  • “…a framework for clinical practice that incorporates the bestavailable scientific evidence with the expertise of the clinician and the patient’s preferences and values to make decisions about health care.” (Levin, 2006)

What is research

What is Research?

Process of searching for newknowledge about phenomena

Validates and refines existingknowledge (Burns & Grove, 2007)

Systematic process of inquiry or study

Builds new knowledge through the dissemination of findings

Why research

Why Research???

  • To Describe

    • To identify and understand the nature of nursing phenomena

    • What is the experience of growing up poor in Manhattan?

  • To Explain

    • Clarifies the relationship among phenomena, and why certain events occur

    • What are the factors that supported DSN graduates to pass NCLEX at 95% in 2009?

Why research1

Why Research???

  • To Predict

    • This allows us to estimate the probability of a specific outcome in a given situation

    • There is a statistical difference in baseline patient glucose levels when using basilar method over sliding scale.

  • To Control or Manipulate

    • If we can predict, the next goal would be to control or manipulate the situation to produce the desired outcome.

    • We can reduce bed sores at all stages by rotating patients every two hours maximum.

Ways we acquire knowledge




Trial and error

Personal experience

Role-modeling & mentoring










Mixed / Other

Ways We Acquire Knowledge

Research defined

Research Defined

  • Research is a systematic, diligent inquiry that is necessary to address:

    • What needs to be known-what is the question, hypothesis, or interest area

    • What research methods are needed to examine this question or phenomena

    • What meaning can be extracted from the study through data analysis to build our knowledge base of that subject

  • Generate outcomes and disseminate new knowledge

Ways to study research

Ways to Study Research

  • By its components (questions, rigors, sampling method, measurement method, etc)

  • Divided into two major types

    • Qualitative

    • Quantitative

  • By the name of the method (experimental, phenomenology, etc)

  • By the philosophy it uses to inquire (positivistic, naturalistic, both, neither)

Burns grove method examine your text

Burns & Grove method: Examine Your Text

  • Table of Contents 7 Ch. 1

  • Ch. 2 = Quantitative Research

  • Ch. 3 = Qualitative Research (philosophy discussed)

  • CH. 4 = tries to address both qualitative and quantitative questions

  • Ch. 5, 6 = Lit review, Study Frameworks & Theory

Examine your text

Examine Your Text

  • Ch. 7 = ethics

  • Ch. 8 = Clarify Designs (quantitative)

  • Ch. 9 = Outcomes Research

  • Ch. 10 = Populations and Sampling for quantitative and qualitative methods

  • Ch. 11 = Measurement of Data quantitative and qualitative

  • Ch. 12 = Understanding Statistics

Examine your text1

Examine Your Text

  • Ch. 13 = Critiquing Research for qualitative (five Standards) and quantitative.

  • Ch. 14 = Building an Evidence Based Practice

Ch 14 evidence based practice

Ch. 14 Evidence Based Practice

  • Research Utilization (RU) may have a lag time for Practice up to 20 years

  • Involves being a Change Agent. (DSN uses the I2E2 model for change in third quarter)

  • Best Evidence by research type

    • Integrative Reviews (many types of designs)

    • Systematic Reviews (focused on a particular type of research designs)

    • Meta-Analysis (has statistical evaluation of quantitative designs).

    • Metasummaries & Metasynthesis (qualitative research)

Hierarchy of evidence compare to florczak article

Hierarchy of EvidenceCompare to Florczak article

  • Level I: A systematic review or RCTs, meta-analysis of many randomized controlled trials (RCTs)

  • Level II: Integrative Reviews of experimental designs

  • Level III: from a well-designed controlled trial without randomization

  • Level IV: From case-control or cohort studies

Hierarchy of evidence compare to florczak article1

Hierarchy of EvidenceCompare to Florczak article

  • Level V: From systematic reviews of descriptive or qualitative studies, metasummaries, metasynthesis,

  • Level VI: a single descriptive or qualitative study

  • Level VII: It is an opinion from authorities on that subject, or expert committee

Recent changes in nursing

Recent Changes in Nursing

  • Page 500, second paragraph, Using ASA 81 mg. in at risk adults

  • Page 517, I.V. flush using 0.9% NS vs. heparin. P & P on page 520.

  • Algorithms on page 524 for tx HTN.

  • I.V. skin prep using chlorhexidine vs. Iodine products like providone-iodine

  • Strait cath urethra prep

Mydsn org nrs 338, NRS 338

  • Evidence Based Research

Research philosophy method positivistic versus naturalistic inquiry

Research Philosophy Method:Positivistic versus Naturalistic Inquiry

  • This is a 100 yearold debate

  • It is often correlated to research methodology

  • It is a philosophy on the way we think about human phenomenon & inquiry (research)

  • We can integrate two different inquiry methodologies, but philosophically they are very different (mixed or blended design)

  • Our philosophy is the foundation for how we design research

Nursing research

Positivistic InquiryNaturalistic Inquiry (Constructivism)Quantitative Triangulated QualitativeSolomon Design Blended DesignsPost-modern -four group design - use quantitative -pretest-treat-post test Intervention Res & qualitative -research self -pretest-no treat- post test methods -novel sounding -no pre- no treat- post test lacks theory -random group Quasi-ExperimentalGrounded Theory Phenomenology -validated tools -two of three -theory building - descriptiveExp. controls -Basic Social Process - interpretive - hermeneuticDescriptiveExperimental Design - quantitative orEthnography -random sample qualitative methods -living in the experience -control group -cultural immersion -a treatment given Outcome Research Case StudyEpidemiology (humans & Ds) -single-double cases Analytic Epi -In-depth analysis Descriptive Epi - comparative analysisAction ResearchAdequate time commitmentCollaborative effortOpenness to changeQuality of data collection and analysis Impact on one’s practice

Nursing research

Positivistic InquiryNaturalistic Inquiry (Constructivism)Quantitative Triangulated QualitativeSolomon DesignBlended DesignsPost-modernQuasi-ExperimentalGrounded Theory PhenomenologyConstant Comparative AnalysisDescriptiveExperimental DesignEthnographyCase StudyScientific Rigors by DesignQuantitative Research RigorValidity & Reliability (internal-external) Qualitative Research RigorConceptual Framework DevelopedDescriptive Vividness Statistical InferenceMethodological CongruenceGeneralizabilityAnalytical PrecisenessTemporalityTheoretical Connectedness Selection and BiasHeuristic RelevanceMeasurement validity / reliabilityTrustworthiness, Credibility, Controlling confoundersand AuditabilityAppropriate study design for the questionsConfirmability, transferabilityStylistic & Personal Relevance, Heuristic

Nursing research

Sample Size by DesignPositivistic Inquiry Naturalistic Inquiry (Constructivism)Quantitative Triangulated QualitativeSolomon DesignBlended DesignsPost-modern Power Analysis 20-40 1 Quasi-ExperimentalGrounded Theory Phenomenology >40 10-1000 10+saturation (10-30) DescriptiveExperimental Design1-12EthnographyPower Analysis 1Case Study1-2Action Research?-100

Assumptions of positivistic thinking

Assumptions of Positivistic Thinking

  • Reality is singular, tangible, & and can be dissected

  • The researcher and those being studied are independent

  • Time and context-free generalizations are possible

  • Inquiry is value-free



value free






Assumptions of positivistic thinking1

Assumptions of Positivistic Thinking

  • There are real causes or at least high probability of a relationship.

  • We believe we can have independent and dependent variables as separate entities

  • Validity of a design is very critical to results



value free



cause &






Assumptions of positivistic thinking2

Assumptions of Positivistic Thinking

  • Reliability is based on how the design is reproducible

  • Generalizability is related to good internal validity and reliability with comparable samples

  • Hypothesis testing










& effect





Assumptions of naturalistic inquiry

Assumptions of Naturalistic Inquiry

  • Realities are multiple, pluralistic, and holistic

  • The researcher cannot really be separated from those being studied and relation-ships are explained

  • hypotheses are time and context bound - they are only working statements

multiple realities




is a focus



& subject


Assumptions of naturalistic inquiry1

Assumptions of Naturalistic Inquiry

  • All entities are in a state of mutual simultaneous shaping

  • Inquiry is value-bound

  • Validity is designed into the process

  • Reliability & general- izable are not concepts of value with this thinking

multiple realities

inquiry is value bound




is a focus



& subject




Differences in scientific rigor positivistic naturalistic


Internal and external reliability

Hypothesis testing

Statistical inferences

Independent and dependent variables

Variable controls


Descriptive Vividness

Methodological Congruence

Analytical Preciseness

Theoretical Connectedness

Heuristic Relevance


Differences in Scientific Rigorpositivisticnaturalistic

Data collection difference positivistic naturalistic


surveys, questionnaires

objective assessment & identification

Measure the dependent variable

Convert to numeric symbols

Apply statistical inferences to numbers

Large sample sizes help withconfidence levels


is the investigator by interview, focus groups, & observation

Data is subjective and objective. It is collected & not measured

Themes or clusters are identified and data is sorted in a theme analysis

The themes are supported by participants or experts

Data Collection Differencepositivisticnaturalistic

Differences in results positivistic naturalistic

Statistical significance for pre-post treatment

Statistical correlations & relationships identified

Probability of errors & confidence identified

Causal relationships

The exploration & description of a phenomenon

Identification of linkages, relationships, or interpretations based on theory connections

Results are themes, clusters of ideas, or theory constructs

Differences in Results positivisticnaturalistic

Positivistic discussion of results

Positivistic Discussion of Results

  • 250 nurses were surveyed with an 80% response rate or N=200. Questions were rated using the Likert 5 scale. Question 1 had a mean of 4.2 with a S.D. of 0.5 suggesting the nurses had favorable opinions about continuing education. Compared to a 1994 survey asking the same question, there was a statistical difference that was less favorable (mean 3.1, S.D. 0.7, p<.05)

Naturalistic description

Naturalistic Description

  • I sat in the classroom as a peripheral member staying as unobtrusive as possible. The instructor came out from behind her desk, sitting on the edge as she opened with a question that brought all eyes in the room to meet her own eyes. She paused - looked at the eyes of the students.

  • The instructor displayed immediacy from the moment she started the class.

Ethics and research ch 7

Ethics and Research (Ch. 7)

  • Starts with the study purpose, design, methods of measurement, and subjects

  • Guidelines for all of these

  • It is still a concern today

  • More recent ethical issues are:

    • Fabrication of a study

    • Falsification or forging of data

    • Dishonest manipulation of the design or methods

    • Plagiarism

  • 50% of the top 50 research institutions in US have been investigated for research fraud

Ethical problems in history

Ethical Problems in History

  • Nazi medical experiments (1933-1945)

  • Tuskegee syphilis study by the USPHS (1932-1972)

  • Willowbrook study (1950-1970) Hepatitis study

  • Jewish Chronic Disease Hospital study with live CA cells in 1960s

Ethical problems in history1

Ethical Problems in History

  • University –Atomic Energy Government Exp.

    • 18 men and women injected with plutonium to determine body distribution (at the time said to be terminal) 1945-47

    • 20 subjects ages 63-83 given doses of radioactive radium and thorium inj. or oral. 1961-65

    • 64 male inmates at Washington St. Prison had testicular radiation to determine the smallest does to makes someone sterile. 1963-70

    • 125 retarded residents were fed radioactive ir9n and calcium to see if a diet rich in cereal would block the digestion of those two minerals. 1946-56

Nuremberg code 1949

Nuremberg Code-1949

  • Voluntary consent

  • Must yield fruitful results for society

  • Anticipated results justify the type of experiment

  • Avoids all unnecessary physical-mental injury

  • Cannot do studies that have a known injury or death unless the exp. Physician is a subject

  • Risk does not out weight humanitarian benefit

  • Proper precautions to prevent injury, dis., death

  • Conducted by qualified persons

  • Subjects can always stop the study

  • Researcher must always be ready to stop the study (risk)

Declaration of helsinki 1964 84

Declaration of Helsinki-1964-84

  • Differentiated therapeutic vs. non-therapeutic research

    • Clinical vs. Basic

  • Greater care to protect subjects in non-therapeutic research

  • There must be a strong, independent justification for exposing a healthy vol. to substantial risk

  • The investigator is to protect the health and life of research subjects

The belmont report three ethical principles

The Belmont ReportThree Ethical Principles

  • Principle of respect for persons

    • Right to self determination and freedom to participate or not

  • Principle of Beneficence

    • Do no harm to others

  • Principle of Justice

    • Treat everyone fairly without discrimination

  • Led to USDHHS Code on Ethics

    • Title 45, Part 46 (45 CFR 46)

    • Office of Human Subjects Research (OHSR) within NIH


Institutional review board irb

Institutional Review Board (IRB)

  • Provides oversight on all ethical issues related to someone doing research

  • Consent forms (voluntary subjects)

  • Disclosure forms

  • Confidentiality

  • Compensation disclosure

  • Ethics documented in the research

  • Accountability to rules, regulations, and legal entities

  • Protects at risk populations

The literature review

The Literature Review

  • Primary Sources

  • Secondary Sources

  • Theoretical literature

  • Empirical (Research) literature

  • Evidence Based Research Sites

Definition of a literature review ch 5

Definition of a Literature Review (Ch. 5)

  • A systematic and explicit approach to the identification, retrieval, and bibliographical management of independent studies … locating information … synthesizing … developing guidelines …

Purposes of the lit review

Purposes of the Lit. Review

  • Facilitate development of the Conceptual Framework by summarizing knowledge

  • Clarify the research topic

  • Clarify the research problem

  • Verify the significance of the research problem

  • Specify the purpose of the study

  • Describe relevant studies or theories

  • Develop definitions of major variables

  • Select a research design, data measurement, data collection & analysis, & interpret findings

Literature searches

Literature Searches

  • Ebscohost with CINAHL:

  • Log in: DSN

  • Password: evidence


    • NRS 338

    • Data bases

Understanding research designs

Understanding Research Designs

  • Can have confusing terms

  • Research Methodology

    • The entire process from question to analysis

  • Research Design

    • Clearly defined structures within which the study is implemented

    • Is a large blueprint, but must be tailored to the study and then mapped out in detail

Quantitative designs ch 2

Quantitative Designs (Ch. 2)

What are the four types of

Quantitative Designs?

Quantitative designs

Quantitative Designs





Aim to describe, compare, and predict in order to understand or control phenomena

Quantitative designs1

Quantitative Designs

What characterizes true Experimental Research Designs?

True experimental research designs

True Experimental Research Designs

Are characterized by:

  • Random assignment of subjects to groups

  • Comparison of treatment group(s) with a

  • Controlor “business as usual” group

True experimental research designs cont

True Experimental Research Designs (cont.)

Also characterized by …

  • Strict control of extraneous variables

    to obtain true representation of “cause

    and effect”

  • Note: use “causality” language with caution!!! (there is always a P-value)

    • Ex: Smoking and cancer

Randomized controlled clinical trials rct

Randomized Controlled Clinical Trials (RCT)

True Experimental Design

Large N (# of subjects)

Draw subjects from reference population

Randomly assign subjects to treatment/experimental or control group

Examine for baseline equivalence

Multiple sites used for generalizability

Quasi experimental research designs

Quasi-Experimental Research Designs

Are characterized by:

  • Treatment or intervention

  • Comparison of treatment group(s) with a

    controlor “business as usual” group

  • Non-equivalence of groups--not randomly assigned; group assignment often evolves naturally “convenience” sampling)

    • Ex: Pts. on one unit compared to pts. on another

Quasi experimental research designs cont

Quasi-Experimental Research Designs (cont.)

Also are characterized by…

Aiming to represent “cause and effect” in situations where less control over variables exists

Most frequently used design in nursing

Correlational designs

Correlational Designs

  • Descriptive correlational designs

    • Used to describe variables and to examine relationships between or among variables

  • Predictive correlational designs

    • Used to predict value of one variable based on values obtained for another variable

    • Independent variable used to “predict” Dependent variable  Regression

    • Model-testing design

      • Looks at relationships among a # of variables

Correlational designs1

Correlational Designs

  • Descriptive correlational designs

    • Used to describe variables and to examine relationships between or among variables

  • Predictive correlational designs

    • Used to predict value of one variable based on values obtained for another variable

    • Independent variable used to “predict” Dependent variable

Quantitative design concerns

Quantitative Design Concerns

Primary purpose (check question)

Is there a treatment (intervention)

Will the treatment be controlled

Is there a control (untreated) group

Is there a pre or post test (or both)

Is sample random

Will sample be a single group or divided into several groups

Quantitative design concerns 2

Quantitative Design Concerns-2

How many groups will there be

What is the size of each group

Will groups be randomly assigned

Will there be repeated measurements over time or will the data be collected cross-sectionally at one or two points in time

Have extraneous variables been identified and controlled for

What strategies are being used to compare variables or groups

Research question considerations

Research Question Considerations






Hypotheses and research qs

Hypotheses and Research Qs

Hypotheses: Intelligent guesses about predicted relationships

Problem statement  what the issue/concern/problem is and why it should be addressed

Research Qs: “Burning question”

What are criteria for hypotheses ch 4

What are Criteria for Hypotheses? (Ch. 4)


Written in present tense

Include population

Identify variables

Reflect the problem/concern

Are empirically testable

Independent dependent variables

Independent & Dependent Variables

  • Independent (IV)

    • The treatment

    • The intervention

    • That which is manipulated

  • Dependent (DV)

    • Outcome

    • What is being measured

    • The difference

Types of hypotheses simple complex

Types of Hypotheses: Simple & Complex

  • Simple

    • One Independent Variable (IV) and one Dependent Variable (DV)

  • Complex

    • Two or more IVs, two or more DVs, or

      both, being investigated at same time

Hypothesis 1

Hypothesis: #1

Average length of gestation is shorter for infants of mothers who use cocaine than among mothers who use alcohol during the last six months of pregnancy.

Population? IV? DV?

Simple or complex?

Hypothesis 2

Hypothesis: #2

The greater the degree of sleep deprivation, the higher the anxiety levels of intensive care unit patients.

Population? IV? DV?

Simple or complex?

Hypothesis 3

Hypothesis: #3

The total wt. loss of overweight elementary students who follow a reduced calorie diet and exercise 20 minutes four times a week will be greater than those students who do not follow a reduced calorie diet and do not exercise 20 minutes four times a week.

Population? IV? DV?

Simple or complex?

Hypothesis 4

Hypothesis: #4

The degree of stress reported by flight-for-life nurses is greater than the degree of stress reported by ICU nurses.

Population? IV? DV?

Simple or complex?

Name that hypothesis 5

Name that Hypothesis: #5

More domestic violence and levels of anger are reported by veterans who served in the military in Iraq compared to those in the military who served in Afghanistan.

Population? IV? DV?

Simple or complex?

Sample of research topic questions

Sample of Research Topic & Questions

  • Topic: Adolescent sexuality

  • Problem statement: (e.g., pregnancy rates in US are much higher compared to most Western countries)

  • Research Question:

    • Will high school adolescent males report higher levels of comfort with their own sexuality than will females?

  • Hypothesis:

    • Adolescent males in grades 9 – 12 will report statistically higher levels of comfort with their own sexuality than will females in the same grades.

Quantitative design concerns1

Quantitative Design Concerns

  • Primary purpose (check question)

  • Is there a treatment (intervention)

  • Will the treatment be controlled

  • Is there a control group (untreated)

  • Is there a pre or post test (or both)

  • Is the sample a random sample

  • Will the sample be a single group or divided into several groups

Quantitative design concerns 21

Quantitative Design Concerns-2

  • How many groups will there be

  • What is the size of each group

  • Will groups be randomly assigned

  • Will there be repeated measurements

  • Will the data be collected cross-sectionally or over time

  • Have extraneous variables been identified and controlled for

  • What strategies are being used for comparison of variables or groups

Components of study validity

Components of Study Validity

  • Definition: It is an examination of the approximation of truth or falsity of the propositions

    • Statistical Validity (right stats used)

    • Internal Validity (sample represents the population being studied)

    • Construct Validity (concept & Operational def. of variable match, & instrument accuratly measures theoretical constructs it purports to measure.

    • External Validity (methods allow for generalizability)

      • (Cook and Campbell, 1979)

Statistical validity errors

Statistical Validity Errors

  • Violate assumptions about the data

    • Nominal, ordinal, interval, ratio data

  • Type I and Type II errors

  • Need for Power Analysis

    • Predicts the necessary N value

  • Inappropriate use of certain statistics for the various types of data

  • Random irrelevancies in setting

  • Random heterogeneity of respondents

Statistical conclusion validity type i and type ii errors

Statistical Conclusion ValidityType I and Type II Errors

Accept the Null Hypothesis Reject the Null Hypothesis

Reality is: Type I Error

No Desired There is no difference

difference caused by fishing

Reality is: Type II Error, there is

There is a difference often caused Desired

Difference by a low N value

Internal validity

Internal Validity

  • Definition:

    *It is the extent to which the effects detected in the study are a true reflection of reality rather than the result of extraneous variables;

    * The independent variable did have an impact on the dependent variable and it was not by random chance (p value)

Threats to internal validity

Threats to Internal Validity

  • History: Natural events over time impacting the subjects

  • Maturation: A person’s growth in any area impacting his/her response

  • Testing effect caused by subjects remembering previous testing

  • Instrument reliability of treatment

  • Selection process (randomized)

  • Mortality threat

  • Interaction with subjects

  • No equalization of treatment

External validity

External Validity

  • Definition:

    To provide development of the design that allows it to be generalized beyond the sample used in the study.

    Most serious threat is that the results can only be said of the group being studied

Threats to external validity

Threats to External Validity

  • Small N

  • No randomization when it is needed

  • Poor sample representation either by type, geography, or some other characteristic

  • Cannot be replicated for some extraneous variable

Factors influencing sample size

Factors Influencing Sample Size

  • Effect Size

    • The degree to which the phenomenon is present in the population or to which the null hypothesis is false.

    • It is hard to detect an effect from an intervention if the sample is small

  • Type of study conducted

    • Case study, phenomenology, experimental, Descriptive

Factors influencing sample size1

Factors Influencing Sample Size

  • The number of variables

    • This requires a power analysis to determine the necessary N

  • Measurement Sensitivity

    • The ability of the measurement to find what it thinks it is finding.

  • Data Analysis Techniques

    • The various statistics can impact the number of subjects needed.

Types of probability sampling

Types of Probability Sampling

  • Simple Random Sampling (select those with specific characteristics)

  • Stratified Random Sampling (2 or more strata of population)

  • Cluster Sampling (all states, cities)

  • Systematic Sampling (every nth)

  • Random Assignment to Groups (Treatment and Control)

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