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Chapter Thirteen Data Collection and Measurement.
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Transcript of Chapter Thirteen Data Collection and Measurement.
![Page 1: Chapter Thirteen Data Collection and Measurement.](https://reader035.fdocuments.in/reader035/viewer/2022062304/56649e555503460f94b4cfcd/html5/thumbnails/1.jpg)
Chapter ThirteenChapter Thirteen
Data Collection and Measurement
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Measurement• The process by which categories or
numbers are used to reflect or indicate concepts and constructs
• A concept is a general idea not directly observable in the real world
• A construct is a concept specified in such a way that it is observable in the real world
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Levels of a Research Study• Theoretical - interconnected propositions or
statements of relationship between concepts
• Conceptual - statements of relationships between two or more constructs
• Operational - indicates how each of the constructs will be measured or operationalized. It refers to the indicators used to reflect the constructs as well as to the procedures used to collect & analyze data
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Theoretical Substruction
• The dynamic thinking process used to move from the theoretical level to the operational or measurement level of a study
• It illustrates the hierarchical order among the major constituents of a study
• It identifies the foundational elements of a study, determines the relationships among the elements, & presents this in a diagram
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Measurement• Measurement is the linkage between the
conceptual and the operational levels of a research project
• Two key issues in this linkage: validity or the the congruence between a concept and the indicators of the concept, and reliability or the extent to which an instrument yields similar results on repeated measures
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ValidityValidity
• Face validity..on the face of it...
• Content validity…reflects the dimension implied by the concept
• Concurrent validity…correlation of one measure with another
• Predictive validity...predict accurately
• Construct validity…distinguishes participants who differ on the construct
• Internal validity…treatment produces changes in dependent variable
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Validity Cont.
• Internal validity…treatment produces changes in dependent variable
• External validity…extrapolation from study to the other groups in general
• In qualitative research…”credibility” is the issue
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Validity in Qualitative Research
• A qualitative study is credible when it presents descriptions of experiences that the people having had that experience immediately recognize as their own
• … the best test of rigor in qualitative work is when the researcher creates “true-to-life, and meaningful portraits, stories, & landscapes of human experiences…” (Sandelowski, 1993)
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Rigor in Qualitative Research
• Keep careful records
• Avoid the holistic fallacy
• Guard against elite bias
• Don’t be taken over by respondent
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Reliability
• Instruments ability to produce the same results on repeated measures
• Terms such as dependability, consistency, stability & accuracy are often used interchangeably
• accuracy reflects the instrument’s ability to measure the true value (free from random measurement error) being measured
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Reliability in Quantitative Reliability in Quantitative ResearchResearch
• Reliability is a relative term, expressed as a correlation …1.00 (perfect reliability) to 0.00 (absence of reliability)
• Reliability coefficients of .70 are acceptable (Nunnally, 1978)
• Estimates of reliability need to be determined each time the instrument is used
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Three Attributes of Reliability
• Stability
• Internal Consistency
• Equivalence
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Stability
• Concerned with consistency of results with repeated measures
• Test-retest procedures - response should be identical on both occasions assuming the variables measured remain the same at the two testing times
• Gillis (1997) tested the reliability of the ALQ using the test-retest procedure
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Internal Consistency
• Refers to the homogeneity of the instrument or the ability of the items in the instrument to measure the same variable
• Items are strongly correlated to each other
• The > intercorrelations, the > internal consistency
• Measures to test internal consistency: KR-20, item-total correlations, split-half method, cronbach’s alpha
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Equivalence
• Degree of agreement among 2 or more different observers using the same measurement tool, or
• Degree of agreement among 2 or more alternate forms of an instrument or tool
• Determined by correlating the 2 scores with each other
• Interrater reliability may be determined several times in a study
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Reliability in Qualitative Research
• In qualitative research replication is not possible because the circumstances & individuals can never be the same at some later time
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Measurement Error
• Any deviation from the true value
• True value is the underlying exact quantity of a variable at any given time
• Variables change over time & any measure will vary slightly from 1 day to the next
• Measure are made up of the following:Measure=TV+ (SE+RE)
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Measurement Error Cont.
• Systematic error…non-random error that systematically over- or under-estimates a value (eg., persons not answering a question are given the lowest value
• Random error…random fluctuations around the true value. Not a problematic…should average out.
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Tips for Reducing Tips for Reducing Measurement ErrorMeasurement Error
• Take average of several measures
• Use different indicators
• Use random sampling procedures
• Use sensitive measures
• Avoid confusion in wordings
• Error check data carefully
• Reduce subject/experimenter expectations
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Levels of MeasurementLevels of Measurement
The level of measurement achieved is important because it constrains the type of statistical analysis that can be performed on your data.
• Nominal
• Ordinal
• Ratio
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The Effects of Reduced Levels The Effects of Reduced Levels of Measurementof Measurement
• Underestimating the relative importance of a variable if it is poorly measured
• The greater the reduction in measurement precision, the greater the drop in correlations between variables
• Precisely measured variables will appear to be more important than poorly measured ones
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Data Collection• Process of gathering data from identified
participants to answer a research question
• A variety of quantitative & qualitative methods are available depending upon research question
• indexes or scales, biochemical & physiological measures, projective techniques, delphi techniques, unstructured interviews, focus groups, observation sessions, historical documents
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Item AnalysisItem Analysis
• Good indexes “discriminate well”
• Example of test item development– test graded, students divided into upper and
lower quartile– examine performance on each question– select those questions that discriminate best
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Discrimination of ItemsDiscrimination of Items
Percent Correct Each Item
Bottom Top
Question # 25% 25% 1 40.0 80.0
2 5.0 95.0
3 60.0 55.0
4 80.0 80.0
5 10.0 40.0
6 20.0 60.0
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Selecting Index ItemsSelecting Index Items
• Review conceptual definition
• Develop measures for each dimension
• Pre-test index
• Pilot test index
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Tips for Wording Likert Items
• The “and” alert: avoid multiple dimensions
• Strongly Agree on right hand side 9-points– response set issue
• Avoid negatives like “not” simply use negative wording.
• Vary strength of wording to produce variation in response
• Exercise….items for a euthanasia index
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Other ScalesOther Scales
• Semantic Differential: Here a variety of anchors are used and people place themselves or others on a continuum: shy/outgoing; bookworm/social butterfly
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Other Scales Cont.
• Magnitude Estimations: subjects use numbers or line lengths to indicate perceptions. Very good for comparisons: yields ratio level measures. Comparing liking of teachers; seriousness of crimes; liking of one community compared to another one, etc.
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Other Scales (cont’d)
• Visual Analogue Scales (VAS) measure the intensity of participant’s sensations & feelings about the strength of their attitudes, beliefs, & opinions about specific stimuli such as fatigue, pain, health, etc.
• Usually a 100 mm line is used with anchor words or phrases at each end
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Delphi technique
• A panel of experts used for multiple data collection, analysis and processing
• Obtains the opinions of experts without the financial cost or inconvenience of bringing expert
• opinions of a variety of experts are condensed into precise statements people together
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Physiological Measures
• Particularly appropriate in studies designed to assess the impact of nursing interventions on bodily functions
• Provide objective & sensitive measurements that are difficult for the participant to distort
• e.g. vital signs, % body fat, muscle strength, salivary enzyme levels, serum glucose, etc.
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Observational Measurement• Well suited to phenomena that are best viewed from
a holistic rather than a reductionistic perspective
• Observations maybe structured, unstructured, or semi-structured; occur in natural or controlled settings
• To be scientific they must meet four critieria: consistent with study objectives; systematic & standard plan for recording; checked & controlled; related to scientific concepts or theories
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Interviews
• A face-to-face verbal interaction to illicit information from the respondent usually through direct questioning
• structured, semi-structured, nonstructured
• Advantage of probing, in-depth data, used with participants who are not literate
• Limited by time, cost , sample size