1 Research the Role of Statistics 2

1. Research & the Role of Statistics 2. Variables & Levels of Measurement

1. The Structure of Research & The Role 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)

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

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 cell phones?

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

2. Variables & Levels of Measurement § Reminder: § 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

3 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

3 Levels of Measurement Scales for Measuring Students’ Living Arrangements A *With parents *w/Roommates *Apartment *Dorms *House *Other B *With parents *Dorms *House C *With parents *Away from Home D *With parents *Dorms *House *Apartmnt *Other

3 Levels of Measurement Scales for Measuring Students’ Living Arrangements A *With parents *w/Roommates *Apartment *Dorms *House *Other NOT MUTUALLY EXCLUSIVE B *With parents *Dorms *House C *With parents *Away from Home D *With parents *Dorms *House *Apartmnt *Other

3 Levels of Measurement Scales for Measuring Students’ Living Arrangements A *With parents *w/Roommates *Apartment *Dorms *House B *With parents *Dorms *House *Other NOT MUTUALLY NOT EXCLUSIVE EXHAUSTIVE C *With parents *Away from Home D *With parents *Dorms *House *Apartmnt *Other

3 Levels of Measurement Scales for Measuring Students’ Living Arrangements A *With parents *w/Roommates *Apartment *Dorms *House B *With parents *Dorms C *With parents *Away from Home *House *Other NOT MUTUALLY NOT EXCLUSIVE EXHAUSTIVE HOMOGENOUS D *With parents *Dorms *House *Apartmnt *Other

3 Levels of Measurement Scales for Measuring Students’ Living Arrangements A *With parents *w/Roommates *Apartment *Dorms *House B *With parents *Dorms C *With parents *Away from Home *House D *With parents *Dorms *House *Apartmnt *Other NOT MUTUALLY NOT EXCLUSIVE EXHAUSTIVE HOMOGENOUS O. K.

3 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

3 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

3 Levels of measurement 3. 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

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.