Variables and Hypotheses

Variables

• Concepts in the political world

  • Constant: doesn’t change

  • Why does the dependent variable change?

  • Independent variable: influences the change

  • Relationships:

    • Time based (independent changes first then dependent)

    • Most dependent variables have multiple independent variables that affect them

Types of Variables

1. Antecedent Variables

   • Comes before the typical relationship

   • An independent variable that predicts a dependent variable

2. Intervening Variables

   • Things that can't really be measured (e.g., civic duty)

   • Noted through literature review

Causation vs. Correlation

• Understand the difference.

Hypothesis

• Educated guesses that link variables together

  • Difference between theory and hypothesis

    • Poli-sci focuses on theories which generalize how the world works

    • Have already been tested

    • Hypothesis focuses on how specific events relate to specific circumstances

Measurement

• Operational Definition: necessary for measuring research

  • Example (Education): years of schooling

Reliability and Validity

• Reliability

  • Sources must be reliable: with repeated use, you get the same data

• Validity

  • Measured correctly

    • Internal Validity: accurately measuring what is happening in the project

    • External Validity: Is the situation accurate to how it would be experienced in the real world

Levels of Measurement

• Four Levels of Measurement:

  1. Nominal - names something (gender)

     • Can be discussed qualitatively or quantitatively

  2. Ordinal - suggests an order/quantity

  3. Interval - gaps in between matter (years of education)

  4. Ratio - absolute zero (prominent in chemistry and physics)

Sampling Definitions

• Sample - group studied

• Population - must define statistical population / all interesting topics

• Sampling Frame - list that contains elements of population

Sample Statistics vs Population Parameters

• Sample statistics represents parameter (theoretically representative average)

• Parameters - average if you asked everyone

• True vs. Accurate

  • Is the sample representative of the population?

Types of Samples

1. Simple Random Sample

2. Systematic Sample

3. Probability Sample

4. Stratified Sample

5. Cluster Sample

Importance of Sampling

• Infer about a larger group that there is not time to study

• Statistical Significance

Extra Notes on Public Opinion Polls

• Samples do not account for full population

• Use margins of error to express data

• Maintain unbiased samples for accuracy

Non-Representative Sampling

• Purpose sampling

  • Picking relevant observations that may not represent the entire population

• Convenience sampling

• Quota Sample

• Snowball sample

Statistical Inference

• Probability distribution and expected value

• Normal Distribution and Confidence Interval

Spurious Relationships

• Unseen factors causing changes in both x and y.

Establishing Causation

1. Time

2. Covariation

3. Eliminate/control other possible causes

Research Designs

• Experiments: show causation

  • Randomization and control groups

  • Field experiments: realistic treatment

  • Natural experiments: researchers observe naturally occurring events

• Observational Studies: controlling occurs after data collection

Types of Studies

• Case Study

• Small-n Study

• Large-N Study

Qualitative Research Design

• Plan for collecting and analyzing data

• Case Selection Types

Comparing Cases

1. Method of Difference

2. Method of Agreement

3. Most Similar vs. Most Different

Validity in Qualitative Research

• Cause and Effect: start with outcomes and work backwards to causes

Data Collection Methods

• Interviews

  • Types: Anonymous, background, off the record

• Working with Documents

• Observation and Ethnography

Ethics in Research

• Types of record (on the record, on attribution, etc.)

Quantitative Research Design

• Quantitative data: use of numbers

Randomized Experiments

• Types: Control/experimental group, Post test, Pre test, etc.

Other Experiment Types

• Field Experiments

• Natural Experiments

• Quasi-Experiments