Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
A Mann-Whitney spatial scan statistic for continuous data Lionel - - PowerPoint PPT Presentation
A Mann-Whitney spatial scan statistic for continuous data Lionel - - PowerPoint PPT Presentation
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results A Mann-Whitney spatial scan statistic for continuous data Lionel Cucala , Christophe Dematte August 24th 2010 Introduction 1-Potential clusters 2-A
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Outline
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Outline
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
A data set to analyze
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
A data set to analyze
2000 4000 6000 8000 10000 18000 20000 22000 24000 26000 long[1:339] lat[1:339]
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
A data set to analyze
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
A data set to analyze
➨ 339 dairy farms located in France.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
A data set to analyze
➨ 339 dairy farms located in France. ➨ Somatic individual score (indicator for a disease called mastitis).
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
A data set to analyze
➨ 339 dairy farms located in France. ➨ Somatic individual score (indicator for a disease called mastitis). ➨ Marked point process : (Xi, Ci), i = 1, · · · , n where Xi ∈ A ⊂ Rd and Ci ∈ R.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Definition : Cluster= geographical area where the continuous variable is higher than outside.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Definition : Cluster= geographical area where the continuous variable is higher than outside. Question : Are there one or more clusters ? Where ?
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The null hypothesis
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The null hypothesis
➨ We attempt to reject H0 : (C1, · · · , CN) independent and identically distributed.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The null hypothesis
➨ We attempt to reject H0 : (C1, · · · , CN) independent and identically distributed. ➨ Goals : detecting cluster(s) and testing the significance according to H0.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The null hypothesis
➨ We attempt to reject H0 : (C1, · · · , CN) independent and identically distributed. ➨ Goals : detecting cluster(s) and testing the significance according to H0. Two steps :
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The null hypothesis
➨ We attempt to reject H0 : (C1, · · · , CN) independent and identically distributed. ➨ Goals : detecting cluster(s) and testing the significance according to H0. Two steps :
- defining the set of potential clusters.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The null hypothesis
➨ We attempt to reject H0 : (C1, · · · , CN) independent and identically distributed. ➨ Goals : detecting cluster(s) and testing the significance according to H0. Two steps :
- defining the set of potential clusters.
- choosing a concentration index.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The null hypothesis
➨ We attempt to reject H0 : (C1, · · · , CN) independent and identically distributed. ➨ Goals : detecting cluster(s) and testing the significance according to H0. Two steps :
- defining the set of potential clusters.
- choosing a concentration index.
Statistic : maximal concentration among potential clusters.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The null hypothesis
➨ We attempt to reject H0 : (C1, · · · , CN) independent and identically distributed. ➨ Goals : detecting cluster(s) and testing the significance according to H0. Two steps :
- defining the set of potential clusters.
- choosing a concentration index.
Statistic : maximal concentration among potential clusters. Significance estimated by a Monte-Carlo procedure.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Outline
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Outline
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Fixed-shape potential clusters
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Fixed-shape potential clusters
➨ Circles centered on one event, another event on the circumference.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Fixed-shape potential clusters
➨ Circles centered on one event, another event on the circumference. ➨ Elliptic clusters, with given orientation and shape (2D only).
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Graphs G(δ) associated to the point process :
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Graphs G(δ) associated to the point process : ➨ Vertices : {1, · · · , n}.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Graphs G(δ) associated to the point process : ➨ Vertices : {1, · · · , n}. ➨ Edges : {(i, j) : d(xi, xj) ≤ δ, 1 ≤ i < n, i < j ≤ n}.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
−0.5 0.0 0.5 1.0 1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 x y
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
−0.5 0.0 0.5 1.0 1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 x y
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
−0.5 0.0 0.5 1.0 1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 x y
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
−0.5 0.0 0.5 1.0 1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 x y
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
−0.5 0.0 0.5 1.0 1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 x y
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
−0.5 0.0 0.5 1.0 1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 x y
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
−0.5 0.0 0.5 1.0 1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 x y
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
−0.5 0.0 0.5 1.0 1.5 −1.0 −0.5 0.0 0.5 1.0 1.5 2.0 x y
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
➨ Connected component of the edge i in G(δ) : Ni(δ).
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
➨ Connected component of the edge i in G(δ) : Ni(δ). ➨ Ai(δ) = {x ∈ A : ∃j ∈ Ni(δ), d(x, xj) ≤ δ}.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
➨ Connected component of the edge i in G(δ) : Ni(δ). ➨ Ai(δ) = {x ∈ A : ∃j ∈ Ni(δ), d(x, xj) ≤ δ}. ➨ Potential clusters : C= {Ai(δ) : 1 ≤ i ≤ n, δ ∈ R+}.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Data-based potential clusters
➨ Connected component of the edge i in G(δ) : Ni(δ). ➨ Ai(δ) = {x ∈ A : ∃j ∈ Ni(δ), d(x, xj) ≤ δ}. ➨ Potential clusters : C= {Ai(δ) : 1 ≤ i ≤ n, δ ∈ R+}. ➨ Only n − 1 areas, arbitrarily shaped.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Outline
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Outline
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Concentration indices
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Concentration indices
We evaluate the concentration in Z ⊂ A.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Concentration indices
We evaluate the concentration in Z ⊂ A. ➨ n(Z) = ♯{i : Xi ∈ Z}.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Concentration indices
We evaluate the concentration in Z ⊂ A. ➨ n(Z) = ♯{i : Xi ∈ Z}. ➨ µ(Z) =
1 n(Z)
- i:Xi∈Z Ci.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Concentration indices
We evaluate the concentration in Z ⊂ A. ➨ n(Z) = ♯{i : Xi ∈ Z}. ➨ µ(Z) =
1 n(Z)
- i:Xi∈Z Ci.
➨ σ(Z)2 =
1 n(Z)
- i:Xi∈Z
- Ci − µ(Z)
2.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
We test the presence of a cluster in Z ⊂ A.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
We test the presence of a cluster in Z ⊂ A. ➨ H0 : Ci ∼ f0.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
We test the presence of a cluster in Z ⊂ A. ➨ H0 : Ci ∼ f0. ➨ H1,Z : Ci|Xi ∼ fZ 1 1(Xi ∈ Z) + f¯
Z
1 1(Xi ∈ ¯ Z).
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
We test the presence of a cluster in Z ⊂ A. ➨ H0 : Ci ∼ f0. ➨ H1,Z : Ci|Xi ∼ fZ 1 1(Xi ∈ Z) + f¯
Z
1 1(Xi ∈ ¯ Z). Likelihood ratio : I(Z) = L1,Z(X1, · · · , Xn, C1, · · · , Cn) L0(X1, · · · , Xn, C1, · · · , Cn) 1 1
- µ(Z) > µ(¯
Z)
- .
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The Exponential model
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The Exponential model ➨ H0 : Ci ∼ E
- 1/µ(A)
- .
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The Exponential model ➨ H0 : Ci ∼ E
- 1/µ(A)
- .
➨ H1,Z : Ci|Xi ∼ E(1/µ(Z)
- 1
1(Xi ∈ Z) + E
- 1/µ(¯
Z)
- 1
1(Xi ∈ ¯ Z).
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The Exponential model ➨ H0 : Ci ∼ E
- 1/µ(A)
- .
➨ H1,Z : Ci|Xi ∼ E(1/µ(Z)
- 1
1(Xi ∈ Z) + E
- 1/µ(¯
Z)
- 1
1(Xi ∈ ¯ Z). Likelihood ratio : Iexp(Z) = −n(Z) log
- µ(Z)
- − n(¯
Z) log
- µ(¯
Z)
- .
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The homoscedastic Gaussian model
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The homoscedastic Gaussian model ➨ H0 : Ci ∼ N
- µ(A), σ(A)2
.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The homoscedastic Gaussian model ➨ H0 : Ci ∼ N
- µ(A), σ(A)2
. ➨ H1,Z : Ci|Xi ∼ N
- µ(Z), σ2
1,Z
- 1
1(Xi ∈ Z) +N
- µ(¯
Z), σ2
1,Z
- 1
1(Xi ∈ ¯ Z)
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The homoscedastic Gaussian model ➨ H0 : Ci ∼ N
- µ(A), σ(A)2
. ➨ H1,Z : Ci|Xi ∼ N
- µ(Z), σ2
1,Z
- 1
1(Xi ∈ Z) +N
- µ(¯
Z), σ2
1,Z
- 1
1(Xi ∈ ¯ Z) where σ2
1,Z = n(Z)σ(Z)2+n(¯ Z)σ(¯ Z)2 n
.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The homoscedastic Gaussian model ➨ H0 : Ci ∼ N
- µ(A), σ(A)2
. ➨ H1,Z : Ci|Xi ∼ N
- µ(Z), σ2
1,Z
- 1
1(Xi ∈ Z) +N
- µ(¯
Z), σ2
1,Z
- 1
1(Xi ∈ ¯ Z) where σ2
1,Z = n(Z)σ(Z)2+n(¯ Z)σ(¯ Z)2 n
. Likelihood ratio : Ihomgau(Z) = 1 σ2
1,Z
.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The heteroscedastic Gaussian model
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The heteroscedastic Gaussian model ➨ H0 : Ci ∼ N
- µ(A), σ(A)2
.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The heteroscedastic Gaussian model ➨ H0 : Ci ∼ N
- µ(A), σ(A)2
. ➨ H1,Z : Ci|Xi ∼ N
- µ(Z), σ(Z)2
1 1(Xi ∈ Z) +N
- µ(¯
Z), σ(¯ Z)2 1 1(Xi ∈ ¯ Z).
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Likelihood-based indices
The heteroscedastic Gaussian model ➨ H0 : Ci ∼ N
- µ(A), σ(A)2
. ➨ H1,Z : Ci|Xi ∼ N
- µ(Z), σ(Z)2
1 1(Xi ∈ Z) +N
- µ(¯
Z), σ(¯ Z)2 1 1(Xi ∈ ¯ Z). Likelihood ratio : Ihetgau(Z) = −n(Z) log
- σ(Z)2
− n(¯ Z) log
- σ(¯
Z)2 .
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
No distribution assumption : Mann-Whitney test
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
No distribution assumption : Mann-Whitney test ➨ Rj is the rank of Cj among the Ci, 1 ≤ i ≤ n.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
No distribution assumption : Mann-Whitney test ➨ Rj is the rank of Cj among the Ci, 1 ≤ i ≤ n. ➨ RS(Z) =
i:Xi∈Z Ri.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
No distribution assumption : Mann-Whitney test ➨ Rj is the rank of Cj among the Ci, 1 ≤ i ≤ n. ➨ RS(Z) =
i:Xi∈Z Ri.
➨ Under H0, E
- RS(Z)
- = M(Z) = n(Z)(n+1)
2
.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
No distribution assumption : Mann-Whitney test ➨ Rj is the rank of Cj among the Ci, 1 ≤ i ≤ n. ➨ RS(Z) =
i:Xi∈Z Ri.
➨ Under H0, E
- RS(Z)
- = M(Z) = n(Z)(n+1)
2
. ➨ Under H0, Var
- RS(Z)
- = V (Z) = n(Z)n(¯
Z)(n+1) 12
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
No distribution assumption : Mann-Whitney test ➨ Rj is the rank of Cj among the Ci, 1 ≤ i ≤ n. ➨ RS(Z) =
i:Xi∈Z Ri.
➨ Under H0, E
- RS(Z)
- = M(Z) = n(Z)(n+1)
2
. ➨ Under H0, Var
- RS(Z)
- = V (Z) = n(Z)n(¯
Z)(n+1) 12
➨ Under H0, RS(Z)−M(Z) √
V (Z)
− →
d
N(0, 1).
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
No distribution assumption : Mann-Whitney test ➨ Rj is the rank of Cj among the Ci, 1 ≤ i ≤ n. ➨ RS(Z) =
i:Xi∈Z Ri.
➨ Under H0, E
- RS(Z)
- = M(Z) = n(Z)(n+1)
2
. ➨ Under H0, Var
- RS(Z)
- = V (Z) = n(Z)n(¯
Z)(n+1) 12
➨ Under H0, RS(Z)−M(Z) √
V (Z)
− →
d
N(0, 1). Irank(Z) = RS(Z) − M(Z)
- V (Z)
.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Outline
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Outline
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The farms data set
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The farms data set
2000 4000 6000 8000 10000 18000 20000 22000 24000 26000 long[1:339] lat[1:339]
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The farms data set
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
The farms data set
2000 4000 6000 8000 10000 18000 20000 22000 24000 26000 long[1:339] lat[1:339]
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Astronomical data
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Astronomical data
Observation of a cubic part of the Universe : (20 Mpc)3 .
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Astronomical data
Observation of a cubic part of the Universe : (20 Mpc)3 . 1 Mpc = 3 × 1022 metres .
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Astronomical data
Observation of a cubic part of the Universe : (20 Mpc)3 . 1 Mpc = 3 × 1022 metres . ➨ Locations of the galaxies : X1, · · · , Xn.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Astronomical data
Observation of a cubic part of the Universe : (20 Mpc)3 . 1 Mpc = 3 × 1022 metres . ➨ Locations of the galaxies : X1, · · · , Xn. ➨ Light intensities : C1, · · · , Cn.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Astronomical data
Observation of a cubic part of the Universe : (20 Mpc)3 . 1 Mpc = 3 × 1022 metres . ➨ Locations of the galaxies : X1, · · · , Xn. ➨ Light intensities : C1, · · · , Cn. Goal : detecting areas where galaxies are ”redder”.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Light intensities
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Light intensities
Color Frequency 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 50 100 150
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Astronomical data
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Astronomical data
z x y
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Conclusion
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Conclusion
➨ Graph-based possible clusters, useful in 3D or for multidimensional data.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results
Conclusion
➨ Graph-based possible clusters, useful in 3D or for multidimensional data. ➨ The MW concentration index is hypothesis-free.
Introduction 1-Potential clusters 2-A Mann-Whitney concentration index 3-Results