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FEB 6

Lecture 7

Types of Variables

- Categorical

- Nominal values

- Can’t make a ranking w/values

- Just different from each other

- Ex. religious affiliation, city of residence

- Ordinal

- Values that can be categorized (by rank/order)

- Distances between values is not equal

- Ex. feeling thermometers, party identification

- Continuous

- Distances between values are known and has meaning

- Equal-unit spacing

- Distances between values is equal and meaningful

- Ex. age, time

Notation

- n = the # of cases/observations

- Y-bar or μ = mean

- σ / SD = standard deviation

- σ² = variance

- Typically denote a variable as Y when doing descriptive statistics

- Doesn’t matter if variable is our DV or IV

Descriptive Statistics

- Need ways to describe data

- Learn about the distribution

- Ex. what do the set of values for the variable look like?

- Central Tendency tells us about the “typical value” of a variable at the center of the distribution

- Mode

- “Modal response”

- Most common value, most “popular”

- Mostly used for describing central tendency of categorical variables

- Mean (Y-bar or μ)

- “Average” or “expected value” from a distribution

- Guesses the value of a variable from a case

- The best choice if there is little info

- Can be affected by outliers

- Sum of Y values divided by n

- Denoted as Y-bar or μ

- Median

- Middle/center of the distribution

- The value at the 50th percentile

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