Quantitative Research

Quantitative Research

1. Goals, principles & processes

2. Operationalization & measuring variables: ex: job satisfaction

3. Examining correlations

4. Using correlation coefficients

Goals

• Identify General Patterns and Relationships

• Testing Theories

• Making Predictions

Principles of Quantitative Research

• Generality (relationship holds across a wide range of different cases of a population)

• Parsimony (as few variables as possible should explain as much as possible)

Direct contrast to qualitative but also comparative research

Example: study on income difference in US (how to become rich?)

• Quantitative approach: search for individual level attribute with strongest relation to income level (race, education, income of father etc.). Assumption: all cases are more less the same, different sides of the same coin

• Comparative approach: “how different causes combine in complex and sometimes contradictory ways to produce different outcomes” (Ragin 1994: 138). Identify diverse ways of succeeding and of failing to achieve material success. It’s not about which variables covary better, but which different pathways do exist!

Process

• Framing: clear definition of population of cases, dependent variable and independent variables (deduced from theory)

• Operationalization: transform concepts/variables into measurable indicators/indices

• Data Collection: conduct survey, use secondary sources• Data Analysis: search for covariation• Interpretation: do covariations found, support theory? do

covariations found, mean causality (which direction?)? Ragin: construction of images, relate image to theory/idea

Terms

Variable: general features that may differ (vary) from one case to the next

Indicator: instrument to measure variable

Index: a single number calculated from different indicators

2. Operationalization & measuring variables

Example: study on job satisfaction (theory testing)

Theory: people are happy, when they can do what they are good at

Cases: employees (specify)

Dependent variable: job satisfaction

Independent variable: match between skills of employee and job characteristics

Job Satisfaction

• INDICATORS:

• Survey of employees (ratings)

• Absenteeism

• Ask supervisors (performance)

Pro vs Con

Level of measurement (yes/no, 1-5, 1-100)

(nominal, ordinal, interval, ratio)

Validity & Reliability

• Validity: appropriateness of a measure (indicator)– Does it measure what it is supposed to

measure?

• Reliability: how much randomness is in a measure?– Will repetition of measurement bring the same

result?

• Defining variables

• Operationalizing them

• Defining your levels of measurement

Most important steps for quantitative research. They decide about the quality of the whole research. Once this is done, the researcher has not much influence on the study (Collecting & processing data is very technical)

3. Examining correlations

• Positive correlation: high values ind. V. and high values dep. V.; low values ind. V. and low values dep. V.

Ex: unemployment – crime rate

• Negative correlation: low values ind. V. and high values dep. V; high values ind. V. and low values dep. V.

Ex: bureaucracy – job satisfaction

Degree of Correlation

• Correlation not in all cases (of thousands) to be found. Does not matter

• Correlation Coefficient– To what degree do variables correlate– Pearson‘s r– varies between -1.00 and +1.00

- 1.00 perfect negative correlation

+1.00 perfect positive correlation

0.0 no correlation at all

Correlation ≠ Causation

• Correlation might be coincidence– If we find shoe size and income covary?

• Correlation might be effect of something else (3rd variable that effects both).– Positive correlation: sun protector / skin

cancer (both high because strength of sun)

• Direction of causation might be unclear– education levels / GNP

Correlation ≠ Causation

Correlation + Theory

suggests causation

4. Using correlation coefficients

• Ex: how to explain life expectancy

• Correlation coefficients can help to compare competing causes (how much variation can be explained by the ind. variable a, how much by b?)

Dep Variable Independent Variable

Life expectancy

Calorie consumption

GNP / capita

Doctors / capita

Life expectancy 1.000 .802 .651 .721

Calorie consumption .802 1.000 .848 .321

GNP per capita .651 .848 1.000 .671

Doctors per capita .721 .321 .671 1.000

causes of higher life expectancy

• Nuitrition seems to be most important.

Calorie consumption highest correlation (.802)

• GNP per capita seems also to play a role (.651). But not independent of calories (.848 correlation). GNP effects via calories

• Doctors/capita (.721) quite high + relatively independent from calories (.321)