CJ 526 Statistical Analysis

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## CJ 526 Statistical Analysis

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**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 • 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?**Terms**• Independent variable (IV): a variable thought to have an effect • Dependent variable (DV): affected variable**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**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**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 . . .**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**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**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)**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**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**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**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**Steps in research (continued)**• Interpreting the results and their applications**Why study statistics?**• Enhanced Informed Decision Making • More Knowledgeable Consumers of Research • Better Producers of Research Two Types of Statistical Techniques Descriptive and Inferential**Statistical techniques to organize and summarize data**• Types of Descriptive Statistics: • Average score • Variability • Tables and graphs • Strength of relationship (correlation)**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**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