Chapter 1: The What and the Why of Statistics

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Chapter 1 The What and the Why of Statistics

• The Research Process
• Asking a Research Question
• The Role of Theory
• Formulating the Hypotheses
• Independent Dependent Variables Causality
• Independent Dependent Variables Guidelines
• Collecting Data
• Levels of Measurement
• Discrete and Continuous Variables
• Analyzing Data Evaluating Hypotheses
• Descriptive and Inferential Statistics
• Looking at Social Differences

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The Research Process
Examine a social relationship, study the relevant
literature
Formulating the Hypotheses
Asking the Research Question
Contribute new evidence to literature and begin
again
Develop a research design
THEORY
Collecting Data
Evaluating the Hypotheses
Analyzing Data
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Asking a Research Question

• What is Empirical Research?
• Research based on information that can be
  verified by using our direct experience.
• To answer research questions we cannot rely on
  reasoning, speculation, moral judgment, or
  subjective preference
• Empirical
• Are women paid less than men for the same types
  of work?
• Not Empirical
• Is racial equality good for society?

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The Role of Theory

• A theory is an explanation of the relationship
  between two or more observable attributes of
  individuals or groups.
• Social scientists use theory to attempt to
  establish a link between what we observe (the
  data) and our understanding of why certain
  phenomena are related to each other in a
  particular way.

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Formulating the Hypotheses

• Hypotheses
• Tentative answers to research questions (subject
  to empirical verification)
• A statement of a relationship between
  characteristics that vary (variables)
• Variable
• A property of people or objects that takes on two
  or more values
• Must include categories that are both exhaustive
  and mutually exclusive

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Units of Analysis

• The level of social life on which social
  scientists focus (individuals, groups).
  Examples
• Individual as unit of analysis
• What are your political views?
• Family as unit of analysis
• Who does the housework?
• Organization as unit of analysis
• What is the gender composition?
• City as unit of analysis
• What was the crime rate last year?

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Types of Variables

• Dependent The variable to be explained (the
  effect).
• Independent The variable expected to account
  for (the cause of) the dependent variable.
• IV ? DV

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Cause and Effect Relationships

• Cause and effect relationships between variables
  are not easy to infer in the social sciences.
  Causal relationships must meet three criteria
• The cause has to precede the effect in time
• There has to be an empirical relationship between
  the cause and effect
• This relationship cannot be explained by other
  factors

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Guidelines for Independent and Dependent Variables

• The dependent variable is always the property you
  are trying to explain it is always the object of
  the research.
• The independent variable usually occurs earlier
  in time than the dependent variables.
• The independent variable is often seen as
  influencing, directly or indirectly, the
  dependent variable.

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Example 1
People who attend church regularly are more
likely to oppose abortion than people who do not
attend church regularly.

• Identify the IV and DV

• independent variable
• dependent variable

Church attendance
Attitudes toward abortion

• Identify possible control variables

Age
Gender
Religious affiliation (Catholic, Baptist,
Islamic)
Political party identification

• Are the causal arguments sound?

• e.g. does party id affect abortion views or vice
  versa?

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Example 2
The number of books read to a child per day
positively affects a childs word recognition.

• Identify the IV and DV

Number of books read

• independent variable
• dependent variable

Word recognition

• Identify possible control variables

Older siblings
Gender
Birth order
Health status

• Are the causal arguments sound?

• Most likely. It is hard to construct an argument
  where a 36 month old child affects the number of
  books his or her parent reads to him/her.

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Collecting Data
Examine a social relationship, study the relevant
literature
Formulating the Hypotheses
Ask the Research Question
Contribute new evidence to literature and begin
again
Develop a research design
THEORY
Collecting Data
Evaluating the Hypotheses
Analyzing Data
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Collecting Data

• Researchers must decide three things
• How to measure the variables of interest
• How to select the cases for the research
• What kind of data collection techniques to use

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Levels of Measurement

• Not every statistical operation can be used with
  every variable. The type of statistical
  operations we employ will depend on how our
  variables are measured.
• Nominal
• Ordinal
• Interval-Ratio

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Nominal Level of Measurement

• Numbers or other symbols are assigned to a set
  of categories for the purpose of naming,
  labeling, or classifying the observations.
• Examples
• Political Party (Democrat, Republican)
• Religion (Catholic, Jewish, Muslim, Protestant)
• Race (African American, Latino, Native American)

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Ordinal Level of Measurement

• Nominal variables that can be ranked from low to
  high.
• Example Social Class
• Upper Class
• Middle Class
• Working Class

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Interval-Ratio Level of Measurement

• Variables where measurements for all cases are
  expressed in the same units. (Variables with a
  natural zero point, such as height and weight,
  are called ratio variables.)
• Examples
• Age
• Income
• SAT scores

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Cumulative Property of Levels of Measurement

• Variables that can be measured at the
  interval-ratio level of measurement can also be
  measured at the ordinal and nominal levels.
• However, variables that are measured at the
  nominal and ordinal levels cannot be measured at
  higher levels.

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Cumulative Property of Levels of Measurement

• There is one exception, though
• Dichotomous variables
• Because there are only two possible values for a
  dichotomy, we can measure it at the ordinal or
  the interval-ratio level (e.g., gender)
• There is no way to get them out of order
• This gives the dichotomy more power than other
  nominal level variables

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Discrete and Continuous Variables

• Discrete variables variables that have a
  minimum-sized unit of measurement, which cannot
  be sub-divided
• Example the number children per family
• Continuous variables variables that, in theory,
  can take on all possible numerical values in a
  given interval
• Example length

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Analyzing Data Descriptive and Inferential
Statistics

• Population The total set of individuals,
  objects, groups, or events in which the
  researcher is interested.
• Sample A relatively small subset selected from a
  population.
• Descriptive statistics Procedures that help us
  organize and describe data collected from either
  a sample or a population.
• Inferential statistics The logic and procedures
  concerned with making predictions or inferences
  about a population from observations and analyses
  of a sample.

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Analyze Data Evaluate Hypotheses
Examine a social relationship, study the relevant
literature
Formulating the Hypotheses
Asking the Research Question
Contribute new evidence to literature and begin
again
Develop a research design
THEORY
Evaluating the Hypotheses
Collecting Data
Analyzing Data
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Begin the Process Again...
Examine a social relationship, study the relevant
literature
Formulating the Hypotheses
Asking the Research Question
Contribute new evidence to literature and begin
again
Develop a research design
THEORY
Collecting Data
Evaluating the Hypotheses
Analyzing Data