Raw Moments - Moments About the Origin/Zero - Central/Mean Moments - Moments About The Mean - (Zeroth/First/Second/Third/Fourth/kth/nth) -  of a Probability Density Function

Definitions

Moment

Raw(R) Moment
(Moment about the origin/zero)

Central(C)/Mean(M) Moment
(Moment about the mean 𝜇)

𝑀𝑘

  • 𝑘𝑡ℎ Raw Moment
  • 𝜇𝑘’ = 𝐄[𝑋𝑘]
  • 𝑘𝑡ℎ Central Moment|
  • 𝜇𝑘 = 𝐄[(𝑋 - 𝜇)𝑘]

𝑀0

  • Zeroth Raw Moment
  • 𝜇0’ = 𝐄[𝑋0] = 1
  • Zeroth Central Moment
  • 𝜇0 = 𝐄[(𝑋 - 𝜇)0] = 1

𝑀1

  • First Raw Moment (Mean)
  • 𝜇1’ = 𝜇 = 𝐄[𝑋1] = 𝐄[𝑋]
  • First Central Moment
  • 𝜇1 = 𝐄[(𝑋 - 𝜇)1] = 0

𝑀2

  • Second Raw Moment
  • 𝜇2’ = 𝐄[𝑋2]
  • Second Central Moment (Variance)
  • = 𝐄[𝑋²] - 𝜇²

    • 𝜇2 = 𝐄[(𝑋 - 𝜇)2]
    • 𝜇2= 𝐄[𝑋2 - 2𝜇𝑋 + 𝜇2]
    • 𝜇2 = 𝐄[𝑋2] - 𝐄[2𝜇𝑋] + 𝐄[𝜇2]
    • 𝜇2 = 𝐄[𝑋2] - 2𝜇𝐄[𝑋] + 𝜇2
    • 𝜇2 = 𝐄[𝑋2] - 2𝜇𝜇 + 𝜇2
    • 𝜇2 = 𝐄[𝑋2] - 𝜇2

𝑀3

  • Third Raw Moment
  • 𝜇3’ = 𝐄[𝑋3]
  • Third Central Moment (Skewness)
  • 𝜇3 = 𝐄[(𝑋 - 𝜇)3]

𝑀4

  • Fourth Raw Moment
  • 𝜇4’ = 𝐄[𝑋4]
  • Fourth Central Moment (Kurtosis)
  • 𝜇4 = 𝐄[(𝑋 - 𝜇)4]

Significance of moments (raw, central, normalized) and cumulants (raw, normalized), in connection with named properties of distributions

Moment
ordinal

Moment

Cumulant

Raw

Central

Standardized

Raw

Normalized

1

Mean

0

0

Mean

2

Variance

1

Variance

1

3

Skewness

Skewness

4

(Non-excess or historical) kurtosis

Excess kurtosis

5

Hyperskewness

6

Hypertailedness

7+

Method of Estimating Moments

Point Estimation:

Resources