convert: conversion functions
In userfriendlyscience: Quantitative Analysis Made Accessible
Description
Usage
Arguments
Details
Value
Author(s)
References
Examples
Description
These are a number of functions to convert statistics and effect size measures from/to each other.
Usage
Arguments
chisq, cohensf, cohensfsq, d, etasq, f, logodds, means, omegasq, or, p, r, t, z
The value of the relevant statistic or effect size.
ncf
The value of a noncentrality parameter of the F distribution.
n, n1, n2, N, ns
The number of observations that the r or t value is based on, or the
number of observations in each of the two groups for an anova, or the total number of participants when specifying a noncentrality parameter.
df, df1, df2
The degrees of freedrom for that statistic (for F, the first one is the numerator (i.e. the effect), and the second one the denominator (i.e. the error term).
proportion
The proportion of participants in each of the two groups in a t-test or anova. This
is used to compute the sample size in each group if the group sizes are unknown.
Thus, if you only provide df1 and df2 when converting
an F value to a Cohen's d value, equal group sizes are assumed.
b
The value of a regression coefficient.
se, sds
The standard error of standard errors of the relevant statistic (e.g. of a regression coefficient) or variables.
minDim
The smallest of the number of columns and the number of rows of the crosstable
for which the chisquare is translated to a Cramer's V value.
lower.tail
For the F and chisquare distributions, whether to get the probability of the lower or upper tail.
akfEq8
When converting Cohen's d to r, for small sample sizes, bias is introduced when the commonly suggested formula is used (Aaron, Kromrey & Ferron, 1998). Therefore, by default, this function uses different equations depending on the sample size (for n < 50 and for n > 50). When akfEq8 is set to TRUE or FALSE, the corresponding action is taken; when akfEq8 is not logical (i.e. TRUE or FALSE), the function depends on the sample size.
var.equal
Whether to compute the value of t or Cohen's d assuming equal variances ('yes'), unequal variances ('no'), or whether to test for the difference ('test').
Details
Note that by default, the behavior of convert.d.to.r depends on the sample size (see Bruce, Kromrey & Ferron, 1998).
Value
The converted value as a numeric value.
Author(s)
Gjalt-Jorn Peters and Peter Verboon
Maintainer: Gjalt-Jorn Peters <gjalt-jorn@userfriendlyscience.com>
References
Aaron, B. Kromrey J. D. & Ferron, J. (1998) Equating "r"-based and "d"-based Effect Size Indices: Problems with a Commonly Recommended Formula. Paper presented at the Annual Meeting of the Florida Educational Research Association (43rd, Orlando, FL, November 2-4, 1998).
Examples
1
2
3
4
5
6
7
8
9
10
11
convert.t.to.r(t=-6.46, n=200);
convert.r.to.t(r=-.41, n=200);
### Compute some p-values
convert.t.to.p(4.2, 197);
convert.chisq.to.p(5.2, 3);
convert.f.to.p(8.93, 3, 644);
### Convert d to r using both equations
convert.d.to.r(d=.2, n1=5, n2=5, akfEq8 = FALSE);
convert.d.to.r(d=.2, n1=5, n2=5, akfEq8 = TRUE);
userfriendlyscience documentation built on May 2, 2019, 1:09 p.m.
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Description Usage Arguments Details Value Author(s) References Examples
Description
These are a number of functions to convert statistics and effect size measures from/to each other.
Usage
Arguments
chisq, cohensf, cohensfsq, d, etasq, f, logodds, means, omegasq, or, p, r, t, z |
The value of the relevant statistic or effect size. |
ncf |
The value of a noncentrality parameter of the F distribution. |
n, n1, n2, N, ns |
The number of observations that the r or t value is based on, or the number of observations in each of the two groups for an anova, or the total number of participants when specifying a noncentrality parameter. |
df, df1, df2 |
The degrees of freedrom for that statistic (for F, the first one is the numerator (i.e. the effect), and the second one the denominator (i.e. the error term). |
proportion |
The proportion of participants in each of the two groups in a t-test or anova. This is used to compute the sample size in each group if the group sizes are unknown. Thus, if you only provide df1 and df2 when converting an F value to a Cohen's d value, equal group sizes are assumed. |
b |
The value of a regression coefficient. |
se, sds |
The standard error of standard errors of the relevant statistic (e.g. of a regression coefficient) or variables. |
minDim |
The smallest of the number of columns and the number of rows of the crosstable for which the chisquare is translated to a Cramer's V value. |
lower.tail |
For the F and chisquare distributions, whether to get the probability of the lower or upper tail. |
akfEq8 |
When converting Cohen's d to r, for small sample sizes, bias is introduced when the commonly suggested formula is used (Aaron, Kromrey & Ferron, 1998). Therefore, by default, this function uses different equations depending on the sample size (for n < 50 and for n > 50). When |
var.equal |
Whether to compute the value of t or Cohen's d assuming equal variances ('yes'), unequal variances ('no'), or whether to test for the difference ('test'). |
Details
Note that by default, the behavior of convert.d.to.r depends on the sample size (see Bruce, Kromrey & Ferron, 1998).
Value
The converted value as a numeric value.
Author(s)
Gjalt-Jorn Peters and Peter Verboon
Maintainer: Gjalt-Jorn Peters <gjalt-jorn@userfriendlyscience.com>
References
Aaron, B. Kromrey J. D. & Ferron, J. (1998) Equating "r"-based and "d"-based Effect Size Indices: Problems with a Commonly Recommended Formula. Paper presented at the Annual Meeting of the Florida Educational Research Association (43rd, Orlando, FL, November 2-4, 1998).
Examples
1 2 3 4 5 6 7 8 9 10 11 | convert.t.to.r(t=-6.46, n=200);
convert.r.to.t(r=-.41, n=200);
### Compute some p-values
convert.t.to.p(4.2, 197);
convert.chisq.to.p(5.2, 3);
convert.f.to.p(8.93, 3, 644);
### Convert d to r using both equations
convert.d.to.r(d=.2, n1=5, n2=5, akfEq8 = FALSE);
convert.d.to.r(d=.2, n1=5, n2=5, akfEq8 = TRUE);
|
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