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The investigation of the distribution and determinants of disease within opulations or cohorts.
Epidemiology
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Study conducted by examining a single phenomenon across multiple populations at a single point in time with no intent for followup in the design.
Cross-sectional design
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Study conducted by following subjects over a period of time, with data collection occurring at prescribed intervals.
Longitudinal study
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The meticulous descriptive exploration of a single unit of study such as a person, family group, commnunity, or other entity.
Case study
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An investigation using a single case or subject in which baseline data are collected, an intervention is applied, and the reponses are tracked over time.
Single-subject design
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Single subject designs that continue to measure the response of the individual as the intervention is withdrawn or withdrawn and reinitiated.
Reversal designs
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Designs that involve the analysis of two variables to describe the strength and direction of the relationship between them.
Correlation study
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Research designed to search for variables measured at one point in time that may forecaset an outcome that is measured at a different point in time.
Prediction study
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Tests of association used to determine whether a set of relationships fits in the real world in the way the relationships are hypothesized in the researcher's model of reality.
Tests of model fit
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A variable that is not measured but is related to each variable in the relationship and may affect the correlation of the data.
Suppressor variable
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A condition in which two variables have an appearance of causality where none exists. This link is invalid when objectively examined.
Spurious relationship
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Descriptive research illuminates an understanding of what is.
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Numbers in a data set that are collected to represent research variables.
Descriptive data
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The initial step in descriptive analysis is to choose the appropriate statistical analysis for the level of measurement of each variable.
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Descriptive questions are designed to describe what is going on or what exists
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Cohort studies examine the following variables:
- Sequences
- Patterns of change
- Growth or trends over time
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Strengths of cross sectional studies:
- Practical and economical
- No waiting for the outcome
- Simple
- Inexpenive
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Limitations of cross sectional studies
- Do not capture changes that occur
- Impractical for the study of rare diseases or uncommon problems
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The purpose of studying single subjects is to assess individuals, with the expectation of generalizing to other individuals in similar situations or conditions.
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A case study is not intended to represent a population but to test theory or demonstrate the effectiveness of a practice from a unique and individual perspective
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Strengths of case studies:
- Provide indepth info
- Changes over time observed
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Limitations of case studies:
- No baseline measurement to provide comparison with the intervention outcome
- difficult to determine whether there is an improvement in outcome becuase causation cannot be inferred
- Interpretation can be biased
- Results cannot be generalized
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Strengths of single subject studies
- useful in exploring behavioral responses
- Flexible
- Explore real changes
- easier to implement
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Limitatinos of single subject studies
- not generalizable
- not considered sufficient evidence for a practice change
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Strengths of correlation studies:
- Relatively uncomplicated to plan and implement
- Researcher flexibility
- Outcomes have practial application in practice
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Limitationsof correlation studies
- Cannot manipulate variables of interest so causality cannot be est.
- Designs lack control and randomization so rival explanations may be posed for relationships
- Suppressor variable--the corelation that is measured may be the result of a suppressor variable-one that is not measured but is related to each varaible in the relationship
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