Mean
Sum of values / number of values
Median
Middle value when sorted; less affected by outliers
Standard Deviation
Measures spread; 68% within ±1 SD, 95% within ±2 SD
Standard Error
SE = SD / √n; decreases with larger sample
Normal Distribution
Bell-shaped, symmetric around the mean
Statistical Significance
p < 0.05 means <5% chance result is due to random chance