Research & the Role of Statistics Variables & Levels of Measurement

The Structure of Research & TheRole of Statistics

Begin with Broad Questions

Most social research originates from some general problem or question

Curious/troubled about some aspect of society

Begin with Broad Questions

Example: What influences how a child does in school? General question that

can’t be adequately addressed by 1 study

Narrow Down, Focus In

Next, we come up with a more specific research question one we can realistically

address Here, a review of the

scientific literature can serve as a guide Tells you what other

researchers have found Gives “bearing” to your

research study

Narrow Down, Focus In

Example: What is the relationship between family structure and school performance?

Narrow Down, Focus In

Also can be stated as a causal theory – an explanation of the

relationships b/t phenomena

Example: Children with more parental support/guidance will tend to perform better in school.

Theory Children with more parental support/guidance will

tend to perform better in school. Underlined terms are concepts – abstract ideas concepts are ambiguous

Operationalize

operationalize – define a concept in a way that it can be measured

Operationalize

Put another way: turning concepts into… variables

something measurable any trait that can change values from

case to case

Some concepts easier to operationalize than others

Examples: Parental support/guidance #

parents in home (1 or 2)

School performance GPA (1 to 4)

OTHER OPERATIONALIZATIONS?

Group Exercise: “Operationalization”

Working with the person (or 2) closest to you, come up with variables (something measurable) that could be used as indicators of the following concepts:

1. Healthy lifestyle (of an individual)

2. Economic health of Duluth

3. Success of UMD grads

Operationalize

Hypothesis: derived from theory statement about a

relationship between variables

therefore: it is more specific/exact than

a theory it is testable

Operationalize Hypothesis example:

Students living in homes with 2 parents/guardians will tend to have higher GPA’s than students from 1-parent households.

Independent variable (x) cause (i.e., # of parents)

Dependent variable (y) effect or outcome measure

(GPA) x y

Observe

Observations allow for hypothesis testing Science is a systematic

method for explaining empirical phenomena

Empirical means measurable & observable

Observe

Research methods are the tools used at this stage How are data to be

sampled & gathered? Lab experiment? Survey? Analysis of existing data?

Observations produce data

Observation vs. Anecdote

Analyze Data & Reach Conclusions

Our focus in this class: hypotheses are tested by

comparing observations to theoretical predictions

Statistical procedures give the ability to tell: whether the data support

our hypotheses & by extension, whether

our theory is supported

Analyze Data & Reach Conclusions

Two classes of statistical techniques:1. Descriptive – used to

summarize/organize/ describe data.

Example: What is the avg. # of hours per week people spend on face book?

Analyze Data & Reach Conclusions

Two classes of statistical techniques:2. Inferential – used to

generalize findings from a sample to a population

Example: polling just a few hundred voters to predict how a presidential election will turn out.

Generalize Back to Questions

What do the results tell us about our original broader question? Determined by:

How theories are operationalized

The nature of the observed sample

Variables 101

VARIABLES are any trait that can change values from case to case

Attribute – specific value on a variable Example: sex has 2 attributes, male & female

Variables ALWAYS should: be exhaustive – variables should consist of all possible

values/attributes have mutually exclusive attributes; no case should be

able to have 2 attributes simultaneously

Levels of Measurement

1. Nominal – mutually exclusive & exhaustive categories that cannot be meaningfully ordered (e.g., sex, religion, political affiliation)– Categories need to be relatively

homogenous

Levels of MeasurementScales for Measuring Students’ Living Arrangements

A B D

*With parents *With parents *With parents

*With roommates *Dorms *Dorms

*Apartment *House *House

*Dorms *Apartmnt

*House *Other

*Other

Levels of Measurement

2. Ordinal – categories can be ranked in addition to being categorized. Example: “I would rather get beat with a lead

pipe than attend this class.” 1 = strongly disagree 2 = disagree 3 = neutral 4 = agree 5 = strongly agree

Levels of measurement

What’s Wrong with This Question: How long have you been attending UMD?

1. 1 to 11 months

2. 1 to 2 years

3. 2 to 3 years

4. 3 to 4 years

5. 5 or more years

Levels of measurement3. Interval-Ratio – categorical units are

equal Examples: prison sentence in months, population

of Duluth, age This level permits all mathematical operations

(e.g., someone who is 34 is twice as old as one 17)

Pointy headed issue Interval = no meaningful zero point Ratio = meaningful zero point DOESN’T MATTER ONE BIT FOR DATA ANALYSIS

SPSS calls both interval and ratio variables “SCALE”

Group Exercise

Research Hypothesis = Males who experience hair loss become more likely to experience depression. What is the IV? What is the level of measurement for this

variable? What is the DV? Operationalize the DV so that it is measured at

the nominal, ordinal, and interval/ratio levels.