power analysis: one-way anova user...
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InVivoStat User Guides – Power Analysis: One-way ANOVA Version 4.0 December 2019
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Power Analysis:
One-way ANOVA
User Guide
InVivoStat User Guides – Power Analysis: One-way ANOVA Version 4.0 December 2019
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Contents
1 Introduction ......................................................................................... 3
2 Analysis procedure .............................................................................. 4 2.1 User based inputs ...................................................................................................................... 4
2.1.1 Select the analysis module ................................................................................................ 4 2.1.2 Select the group means ..................................................................................................... 4 2.1.3 Select the variability estimate ........................................................................................... 5 2.1.1 Significance level ............................................................................................................. 5 2.1.2 Defining the plotting range ............................................................................................... 5 2.1.1 Run the analysis ................................................................................................................ 5
2.2 Dataset based inputs ................................................................................................................. 6 2.2.1 Select the analysis module ................................................................................................ 7 2.2.2 Select the dataset to be analysed ....................................................................................... 7 2.2.3 Select the response to analyse and the treatment factor .................................................... 7 2.2.4 Select a transformation for the response ........................................................................... 8 2.2.5 Significance level ............................................................................................................. 8 2.2.6 Defining the plotting range ............................................................................................... 8 2.2.7 Run the analysis ................................................................................................................ 9
3 Output results ...................................................................................... 9
4 Controlling the output ...................................................................... 10
5 Test dataset example output ............................................................ 12 5.1 InVivoStat options (dataset based inputs)............................................................................... 12 5.2 Sample output ......................................................................................................................... 13
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1 Introduction
The Power Analysis modules in InVivoStat are available from the Statistics drop-
down menu entitled ‘Power Analysis’. Methods available include power analyses for
the two-sample t-test (comparison of means) and the overall one-way ANOVA. This
user guide describes the power analysis for the overall one-way ANOVA – powering
for the test of an overall difference between the treatment group means.
There are two interfaces available, depending on how the inputs to the power analysis
are generated:
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2 Analysis procedure
2.1 User based inputs
The steps required to perform an analysis using the user based inputs are described in
this section.
The inputs to the power analysis module include a measure of the variability (standard
deviation or variance), the treatment group means, and the choice of sample size
range. With the ‘user-based inputs’ sub-module, these are all entered manually by the
user.
2.1.1 Select the analysis module
The analysis begins by selecting the
Power Analysis: One-way ANOVA
(User based inputs) from the drop-down
list of available modules:
Power Analysis →
One-way ANOVA →
User based inputs
2.1.2 Select the group
means
Once the dataset has been selected, the
user selects the parameters for the
analysis by clicking on the boxes and
entering values of their choice.
The group means are entered as a
comma separated list.
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2.1.3 Select the variability
estimate
The user should enter an estimate of the
variability, either the standard deviation
or variance can be entered.
The variance estimate can be obtained
from an ANOVA table (the Mean
Square Error).
2.1.1 Significance level
The significance level default is 0.05, or
5%, although this can be changed.
2.1.2 Defining the plotting
range
Part of the output from the power
analysis module is a plot of a set of
power curves. The user can choose the
range of the X-axis (sample size) and
the Y-axis (statistical power) of this
plot.
2.1.1 Run the analysis
Click ‘Submit’ to run the analysis.
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2.2 Dataset based inputs
The steps required to perform an analysis using dataset based inputs are described in
this section.
This version of the One-way ANOVA power analysis module calculates the
variability directly from a dataset. InVivoStat will estimate the variability of a given
response by including a single treatment factor to account for any variability caused
by the treatment effects.
The analysis module accepts data in the single measures format, for example:
Response Treatment
1.17 D0
1.30 D0
1.72 D0
1.17 D0
1.39 D0
1.44 D0
1.60 D0
1.37 D1
1.64 D1
1.53 D1
1.50 D1
1.59 D1
1.77 D1
1.86 D1
1.26 D1
1.64 D1
1.26 D10
1.80 D10
1.19 D10
1.37 D10
1.44 D10
1.92 D10
1.37 D10
1.50 D10
2.06 D3
2.18 D3
1.99 D3
1.69 D3
1.62 D3
2.48 D3
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2.2.1 Select the analysis module
The analysis begins by selecting the
Power Analysis: One-way ANOVA
(Dataset based inputs) module from the
drop-down list of available modules:
Power Analysis →
One-way ANOVA →
Dataset based inputs
2.2.2 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’.
2.2.3 Select the response to
analyse and the treatment factor
Once the dataset has been selected, the
user can select the response variable for
the analysis by clicking on the Response
box and selecting the response to
analyse.
Similarly the user should select the
treatment factor.
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2.2.4 Select a transformation
for the response
Once selected, the user has the option of
applying a transformation to the
response variable, either log10, loge,
square root, arcsine or rank.
2.2.5 Significance level
The significance level default is 0.05, or
5%, although this can be changed.
2.2.6 Defining the plotting
range
Part of the output from the power
analysis module is a plot of a set of
power curves. The user can choose the
range of the X-axis (sample size) and
the Y-axis (statistical power) of this
plot.
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2.2.7 Run the analysis
Click ‘Submit’ to run the analysis.
3 Output results
The output contains the following.
Power curve plot
For the given parameters/variables entered in the module, InVivoStat generates a
power curve to illustrate the relationship between sample size, statistical power and
biologically relevant effect (for a given significance level).
Selected results
A set of summary power analysis results.
Definitions
A set of definitions is given to aid interpretation of the results.
References
A list of references for the methods applied in the analysis.
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4 Controlling the output
The user has the ability to control various aspects of the output. These are available in
the ‘Output Options’ dialogue:
Users can manipulate various plot
characteristics including line size, fonts
and marker size/type.
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The user has control over all text
included on the plots, for example text
position, size and font.
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.
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5 Test dataset example output
5.1 InVivoStat options (dataset based inputs)
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5.2 Sample output
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