Vocabulary
Population vs Sample
Population = entire group. Sample = a subset chosen from it.
POP = ALL · SAMP = PART
Vocabulary
Parameter vs Statistic
Parameter describes the population. Statistic describes a sample.
P→P · S→S
Variables
Categorical vs Quantitative
Categorical = labels / groups. Quantitative = numbers you can add or compare.
CAT = LABELS · QUANT = NUMBERS
Spread
Range & Standard Deviation
Range = max − min (sensitive to outliers). Std dev = average distance from the mean.
Range = MAX − MIN
Formula
Sample Std Dev (sx)
Divide by n−1 (not N). The "−1" corrects for using a sample.
n−1 for SAMPLE
Statistical Questions
What makes it statistical?
A statistical question expects variability in answers — not a single fixed answer.
VARIABILITY = STATISTICAL