Levels of Measurement
Individuals: eye colors, religion, hair color, etc...
Nominal
Contains a few extremely positive (high) values
Positively Skewed Distribution
Mean, Median, Mode
Central Tendency Measures
One category is higher or lower than other categories
Ordinal
Contains only a few extremely low values
Negatively Skewed Distribution
The value that is in the center of middle of the distribution of a variable
Median
Have categories, ranking, and equal intervals
Interval-Ratio
Two peaks in the distribution
Bimodal Distribution
The arithmetic average of all the values (scores) of a variable
Mean
Education (L, M, H), Salary (H, L), Age (Young, Old), 5 (or 7) point scale measure
Ordinal
Bell Shaped, Uni-modal (one mode)
Symmetric Distribution
Subtracting the lowest number from the highest number in a distribution
Range
Education (in years), Salary (in dollars), Age (in years), indexes and scales
Interval Ratio
All the values of the variables are the same
SIngle Value Distribution
The measure of a spread most commonly used in statistical practice when the mean is used to calculate the central tendency. Thus, it measures the spread around the mean.
Standard Deviation