correlation analysis user guide -...

InVivoStat User Guides – Correlation Analysis Version 4.0 December 2019

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Correlation Analysis

User Guide


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Contents

1 Introduction ......................................................................................... 3

2 Dataset format ..................................................................................... 4

3 Analysis procedure .............................................................................. 5 3.1 Select the analysis module ........................................................................................................ 5 3.2 Select the dataset to be analysed ............................................................................................... 5 3.3 Select the responses to analyse and terms to include in the statistical model ........................... 5 3.4 Select a transformation for the responses ................................................................................. 6 3.5 Choice of methodology ............................................................................................................ 6 3.6 Type of test ............................................................................................................................... 6 3.7 Selecting the overall analysis results ........................................................................................ 7 3.8 Run the analysis ........................................................................................................................ 7

4 Output results ...................................................................................... 8

5 Controlling the output ........................................................................ 8

6 Test dataset example output ............................................................ 10 6.1 InVivoStat options .................................................................................................................. 10 6.2 Sample output ......................................................................................................................... 11


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1 Introduction

The Correlation Analysis module in InVivoStat is available from the Statistics

drop-down menu entitled ‘Correlation Analysis’. The user interface is:

The Correlation Analysis module allows the user to perform an assessment of the

correlation between numerical variables. The measures of correlation available

include Pearson, Spearman and Kendall. Pearson measures the strength of the linear

relationship between normally distributed variables, the latter two are non-parametric

measures of association.

Multiple responses can be selected and the statistical results broken down by up to

four different categorisation factors.


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2 Dataset format

The Correlation Analysis module accepts data in the single measures format, for

example:

Response 1 Response 2 Treatment factor Gender

0.147855221 0.530361575 1 M

0.478546674 0.449414718 1 F

0.194974451 0.070003014 1 M

0.748312072 0.686529686 1 F

0.082484998 0.051691636 1 M

0.910153535 0.531666997 1 F

0.103702289 0.606649522 1 M

0.389015849 0.891103806 1 F

0.836681274 0.246116745 2 M

0.794244146 0.488971084 2 F

0.477816935 0.697128782 2 M

0.728864994 0.843433225 2 F

0.607031633 0.880328408 2 M

0.387501297 0.038161635 2 F

0.218561251 0.383582019 2 M

0.61379282 0.901531118 2 F

0.401113994 0.859257567 3 M

0.791579131 0.746496762 3 F

0.523133978 0.383537822 3 M

0.310037853 0.562417047 3 F

0.515408056 0.838273845 3 M

0.912722711 0.61440065 3 F

0.097535273 0.32411548 3 M

0.703568216 0.655027378 3 F

0.820215424 0.128851841 4 M

0.18375973 0.275635145 4 F

0.435744066 0.679079801 4 M

0.826797822 0.835252489 4 F

0.084182403 0.83646952 4 M

0.581541447 0.113312589 4 F

0.587388134 0.841638525 4 M

0.890251907 0.33044708 4 F


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3 Analysis procedure

The steps required to perform an analysis are described in this section.

3.1 Select the analysis module

The analysis begins by selecting the

Correlation Analysis module from the

drop-down list of available modules:

Parametric Analysis →

Correlation Analysis

3.2 Select the dataset to be

analysed

Once the module is selected, the dataset

is chosen from the drop-down list of

available datasets.

Click ‘Submit’.

3.3 Select the responses to

analyse and terms to

include in the statistical

model

Once the dataset has been selected, the

user selects the response variables to

analyse by clicking on the Responses

box and selecting the response variables

to analyse.

Similarly, the user can select up to four

categorisation factors.


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3.4 Select a transformation for

the responses

Once selected, the user has the option of

applying a transformation to the

response variables, either log10, loge,

square root or arcsine.

3.5 Choice of methodology

Three analyses methods are available in

this module: Pearson, Spearman or

Kendall.

3.6 Type of test

The user can choose to perform a one-

sided test (less than or greater than) or a

two-sided test.


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3.7 Selecting the overall

analysis results

There are several results from the

analysis that are available. These are

selected before running the analysis and

include:

1) Estimate of the correlation

coefficient

Generates the estimate of the size of the

correlation (value between -1 and +1).

2) Test statistic

Produces an overall test of the

correlation between the responses.

3) P-value

This option generates a p-value to

assess the statistical significance of the

test statistic.

4) Scatterplot

Generates scatterplots of the responses

plotted against each other. All pairwise

combinations plotted.

5) Matrixplot

Generates a matrixplot of the responses.

6) Significance level

The significance level default is 0.05, or

5%, although this can be changed.

7) By categories and overall

Generate the overall correlation

between the response variables and also

the correlations broken down by the

levels of the categorisation factors.

3.8 Run the analysis

Click ‘Submit’ to run the analysis.


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4 Output results

Responses

InVivoStat identifies the responses being analysed. This section also describes any

transformation that has been applied.

Non-categorised scatterplot of the data

InVivoStat produces scatterplots of the responses. Each combination of the responses

is plotted. This should also be used to identify possible outliers and provides a visual

summary of the overall strength of the relationship between the two responses plotted.

Non-categorised matrixplot of the data

InVivoStat produces a matrixplot that combines the scatterplots of the data into a

single lattice plot.

Table of the results of the non-categorised correlation analysis

InVivoStat produces a table of the results of the overall (non-categorised) correlation

analysis.

Categorised results

When requested, InVivoStat will also generate the above results but broken down into

categories that are the combinations of the levels of the categorisation factors.

References

A list of references for the methods applied in the analysis.

5 Controlling the output

The user has the ability to control various aspects of the output. These are available in

the ‘Output Options’ dialogue:


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Users can manipulate various plot

characteristics including line size, fonts

and marker size/type.

The user has control over all text

included on the plots, for example text

position, size and font.


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The user has control over the colour

scheme employed by InVivoStat,

including an option to produce all plots

in black & white.

Further information on these options can be found in the Getting Started User Guide.

6 Test dataset example output

6.1 InVivoStat options


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6.2 Sample output


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