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An R Companion for the Handbook of Biological Statistics

Salvatore S. Mangiafico

 

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Spearman Rank Correlation

 

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When to use it

Null hypothesis

Assumption

How the test works

See the Handbook for information on these topics.

 

Example

Example of Spearman rank correlation

 

### --------------------------------------------------------------
### Spearman rank correlation, frigatebird example
### p. 212
### --------------------------------------------------------------

Input = ("
Volume   Pitch
 1760    529
 2040    566
 2440    473
 2550    461
 2730    465
 2740    532
 3010    484
 3080    527
 3370    488
 3740    485
 4910    478
 5090    434
 5090    468
 5380    449
 5850    425
 6730    389
 6990    421
 7960    416
")

Data = read.table(textConnection(Input),header=TRUE)


cor.test( ~ Pitch + Volume,
         data=Data,
         method = "spearman",
         continuity = FALSE,
         conf.level = 0.95)

 

Spearman's rank correlation rho

 

S = 1708.382, p-value = 0.0002302

sample estimates:

       rho

-0.7630357

 

 

Simple plot of the data

  

plot(Pitch ~ Volume,
     data=Data,
     pch=16)

 

 

#     #     #

 

 

Graphing the results

See the Handbook for information on this topic.

 

How to do the test

Example of Spearman rank correlation

 

### --------------------------------------------------------------
### Spearman rank correlation, species diversity example
### p. 214
### --------------------------------------------------------------

Input = ("
Town                  State  Latitude  Species
'Bombay Hook'          DE     39.217    128
'Cape Henlopen'        DE     38.800    137
'Middletown'           DE     39.467    108
'Milford'              DE     38.958    118
'Rehoboth'             DE     38.600    135
'Seaford-Nanticoke'    DE     38.583     94
'Wilmington'           DE     39.733    113
'Crisfield'            MD     38.033    118
'Denton'               MD     38.900     96
'Elkton'               MD     39.533     98
'Lower Kent County'    MD     39.133    121
'Ocean City'           MD     38.317    152
'Salisbury'            MD     38.333    108
'S Dorchester County'  MD     38.367    118
'Cape Charles'         VA     37.200    157
'Chincoteague'         VA     37.967    125
'Wachapreague'         VA     37.667    114
")

Data = read.table(textConnection(Input),header=TRUE)

cor.test( ~ Species + Latitude,
         data=Data,
         method = "spearman",
         continuity = FALSE,
         conf.level = 0.95)

 

Spearman's rank correlation rho

 

S = 1111.908, p-value = 0.1526

 

       rho

-0.3626323

 

 

Simple plot of the data

  

plot(Species ~ Latitude,
     data=Data,
     pch=16)

 

 

#     #     #