Sampling and Data Collection Research Methodologies in Allied Health Peg Bottjen, MPA, MT(ASCP)SC.
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Transcript of Sampling and Data Collection Research Methodologies in Allied Health Peg Bottjen, MPA, MT(ASCP)SC.
Research Process
Planning
Hypothesis or Aims
Research Design
Data collection
Organization and Presentation of Data
Data Analysis
Interpretation and Conclusions
Objectives
Upon completion of this unit the student will be able to:
• Outline advantages and disadvantages of three sampling methods • Operationally define the variables in a study • Identify limitations in research studies • Choose the method of data collection that best facilitates proving or disproving a hypotheses or best answers a research question • Explain how a test can be valid yet not reliable.
Boundaries of the Study
Define the terms
Dictionary definitionsex. BMI – wt (kg) / ht2 (m)
Reference to a definitionex. NHANES II study
Operational definitionsex. obesity >95th
percentile
Operational Definition
The operational definition of a variable is a statement of how the researcher in a particular study chooses to measure the variable in question.
Representative Sampling Methods
Randomized – roll of diceArea - locationSystematic – choose from list (every 5th)Volunteer – ask for participantsConvenience – what is available
Sample Size
It depends! Procedures used to
collect data Statistical level of
significance Statistical power Effect size
External Validity
The extent to which the results of an investigation can be generalized to other samples or situations.
Polgar & Thomas-4th Ed. 2001
Internal Validity
The intervention was responsible for the differences or lack of differences observed.
Questionnaire
Open vs Closed questionsScaled questions or statements
Likert scaleStrongly disagree, disagree, no opinion, agree,
strongly agreeSemantic differential
Draw an x at point that best describes your feeling
Powerless Powerful
X
Measurement / Instrumentation
Subjective measurementsRatings or judgments by humans of
quantities or qualities
Objective measurementsMeasurement of physical quantities or
qualities by equipment
Measurement / Instrumentation
Objective measurementData collected by instrumentation
Eg. Blood glucose, MR/CT scans, radiographic image, nuclear medicine scan, activated clotting time (ACT), nutrition screening instrument, stained slide read by expert
Data collected by standardized testsEg. SAT, ACT, GRE, CAT, Myers-Briggs, IQ
test, patient quality of life (SF-36)
Reliability - Precision
The test or assessment measures the same thing every time and results in the same answer every time.
Test-retest – correlates 1st to 2nd Inter-observer – between different observers Internal consistency – between items
measured
Validity - Accuracy
The test or assessment measures what it claims to measure. Sensitivity - % true positive Specificity - % true negative
Test Result Disease Present Disease Absent
+ True + False +
- False - True -
Validity
Predictive value Ability of a measurement to predict the
value of it or another test in the future (prognosis)
What is predictive value of an ACT score to your grade point average in college?
Critical Evaluation of Research
Who comprised the sample? What was the inclusion criteria? What was the exclusion criteria? Was the sample biased? How is the independent variable defined? How is the dependent variable defined? How were validity issues addressed? How were reliability issues addressed?