Describing Variables & Hypotheses Testing

May 26, 2008

Ivan Katchanovski, Ph.D.POL 242Y-Y

Research Hypothesis

• Hypothesis: A basic statement that is tested in research– Based on a political science theory and previous

research– States expected relationship between dependent

and independent variables – This relationship can be tested with empirical data– Hypothesis is either supported or not supported by

research

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Dependent and independent variablesDependent variable

• A variable assumed to depend on or be affected by the independent variable

• A variable which we are interested in explaining– Income level depends on

education level– The level of democracy is

affected the level of economic development

Independent variable

• A variable which presumed to affect the dependent variable

• A variable which we use to explain the dependent variable– Education level increases

personal income – The level of economic

development has a positive effect on the odds that a country is democratic

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Examples of Research Hypotheses

• People with higher income are more likely to vote for the Conservative Party – Pocket book theory of voting behaviour

• Americans are more likely to join civic associations than Canadians are– Political culture theory

• Democratic countries do not wage wars with other democratic countries– Democratic peace theory

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Exercise

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Formulate a hypothesis describing relationship between political views and religiosity. Identify the dependent variable and the independent variable.

Outline of Research Paper

• Political science theory • previous research

• Your research hypothesis• Data• One of datasets from POL 242Y

• Research Method

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Quantitative Analysis

• Univariate - describe a case in terms of a single variable.– Frequency distribution tables and charts

• Bivariate - describe a case in terms of two variables simultaneously.

• Multivariate - analysis of two or more variables simultaneously.

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Frequency distributions

Tables or charts that summarize the distribution of a variable

Economic development level (World dataset)

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Frequency PercentCumulative

Percent Least 22 20.8 20.8Middle 54 50.9 71.7Most 30 28.3 100.0Total 106 100.0

Collapsing categories

Response PercentVery good 5Good 42Poor 21Very poor 6Don’t Know 26Total, percent 100

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Response Percent

Good or better 64

Poor or worse 36

Total, percent 100

Table 1a. How is the government doing in solving the budget crisis?

Table 1b. Evaluation of government performance in solving the budget crisis?

Graphic description of variables

Pie chart Bar chart

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Graphic description of variables

Histogram

Figure1. Age distribution of respondents

Line chart

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Measures Of Central Tendency

• The Mode: Value that occurs most frequently– useful for nominal variables

• The Median: middle value– useful for ordinal and interval-ratio variables

• Other Measures of Position: – Percentiles, deciles and quartiles _

• The Mean: average score X=(Xi)/N – useful for interval-ratio variables

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Skewed Distributions Skew: The extent to which a distribution of scores has a few

scores that are extremely high or extremely low.

Positively skewed distribution Unskewed distribution