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CJ 526 Statistical Analysis

CJ 526 Statistical Analysis. Research methods and statistics. Assumptions 1. there is order in nature 2. every event has an explanation 3. we will never know everything. Terminology. Variable: any trait or characteristic which can take on a range of values

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CJ 526 Statistical Analysis

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  1. CJ 526 Statistical Analysis Research methods and statistics

  2. Assumptions • 1. there is order in nature • 2. every event has an explanation • 3. we will never know everything

  3. Terminology • Variable: any trait or characteristic which can take on a range of values • Hypothesis: Question or statement about the relationship between two or more variables i.e., is there a relationship between number of police on the streets and the crime rate? Between taking medication and improvement?

  4. Terms • Independent variable (IV): a variable thought to have an effect • Dependent variable (DV): affected variable

  5. Terms • Value: • Individual characteristics within the set of the variable • Constant: • Characteristic that does not change in value • Extraneous (EV): • Variable that can affect DV, but one that the researcher is not interested in

  6. Examples • Gender of people in treatment • Variable: • Gender • Values: • Female, male • Social class of patients • Variable: • Social class • Values: • Lower, lower middle, middle, upper middle, upper

  7. Examples of values of variables • Intelligence tests scores • Variable: • Intelligence • Values: • Range from 50 to 160 • Number of prior felony convictions • Variable: • Prior felony convictions • Range from 0 to . . .

  8. Constants--example • Study of serial killers • Gender • (Gender would apply to some medical conditions) • Race • i.e., sickle cell anemia among African Americans—hold race constant

  9. Independent Variable: • Home health visits for at risk mothers • Constant: at-risk • Dependent Variables: Cognitive development, rate of health problems, abuse, school performance, criminal history • Extraneous Variables: • State of the economy, other available services

  10. Terms • Units of analysis: units observed and described to create summary descriptions of all units and to explain differences among them • Individuals • Groups (i.e., families, gangs) • Organizations (hospitals) • Social artifacts (traffic accidents, court cases, prison riots, patient cases)

  11. Terms • Theory: an explanation that systematically organizes observations and hypotheses • Basic vs. Applied Research • Basic--why questions; Applied--solve problems • Cross-sectional vs. Longitudinal Research • Experimental vs. Ex Post Facto Research

  12. Types of research methods • Experiments (manipulation and control) • Surveys (written and interviews) • Field or observational research • Record or archival research (content analysis, secondary analysis) • Case study • Evaluation research

  13. Steps in research • Choosing a research problem • Reviewing the literature: abstracts and journals, books, collected readings, computer searches (NCJRS), CD ROMS, and the internet • Conceptualization of variables, hypotheses, questions

  14. Steps in research • Selecting how to measure variables (operationalization) • Selecting subjects for the study: population and sample • Method: making observations and measurements • Data processing and analysis

  15. Steps in research (continued) • Interpreting the results and their applications

  16. Why study statistics? • Enhanced Informed Decision Making • More Knowledgeable Consumers of Research • Better Producers of Research Two Types of Statistical Techniques Descriptive and Inferential

  17. Statistical techniques to organize and summarize data • Types of Descriptive Statistics: • Average score • Variability • Tables and graphs • Strength of relationship (correlation)

  18. Inferential Statistics • Statistical techniques that allow one to draw conclusions about a larger group based on results from some portion of it • Typical Uses for Inferential Statistical Techniques

  19. Examples of inferential statistics • Program Effectiveness • Short-term and long-term effectiveness of prison boot camp programs • Group differences Do males and females differ in terms of response to a drug? • Theory testing • Prediction • Bail decision making

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