CJ 526 Statistical Analysis

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CJ 526 Statistical Analysis

• Research methods and statistics

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

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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?

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Terms

• Independent variable (IV) a variable thought to
  have an effect
• Dependent variable (DV) affected variable

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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

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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

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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 . . .

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Constants--example

• Study of serial killers
• Gender
• (Gender would apply to some medical conditions)
• Race
• i.e., sickle cell anemia among African
  Americanshold race constant

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• 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

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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)

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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

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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

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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

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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

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Steps in research (continued)

• Interpreting the results and their applications

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Why study statistics?

• Enhanced Informed Decision Making
• More Knowledgeable Consumers of Research
• Better Producers of Research
• Two Types of Statistical Techniques
• Descriptive and Inferential

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

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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

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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