Mode

• most occurring value in the distribution

Median

𝑀

𝑀̅ or 𝑥̃

• the middle value in the sorted distribution
• same as 0.5-quantile, 50th percentile, and 2nd quartile
• is a value 𝑚 that minimizes 𝐄[|𝑋 - 𝑚|]

Arithmetic Mean

𝜇

𝑋̅

• average in distribution
• is a value 𝑚 that minimizes 𝐄[(𝑋 - 𝑚)²]

Harmonic Mean

• average in distribution

Root Mean Square
Quadratic Mean

• ignores negative sign in computing the arithmetic mean

Geometric Mean

• average in distribution

Mid Range

• the average between min and max