UDT {singcar} | R Documentation |
Unstandardised Difference Test
Description
A test on the discrepancy between two tasks in a single case, by comparison
to the mean of discrepancies of the same two tasks in a control sample. Use
only when the two tasks are measured on the same scale with the same
underlying distribution because no standardisation is performed on task
scores. As a rule-of-thumb, the UDT may be applicable to pairs of tasks for
which it would be sensible to perform a paired t-test within the control
group. Calculates however a standardised effect size in the same manner as
RSDT()
. This is original behaviour from Crawford and Garthwaite
(2005) but might not be appropriate. So use this standardised effect size
with caution. Calculates a standardised effect size of task discrepancy as
well as a point estimate of the proportion of the control population that
would be expected to show a more extreme discrepancy and respective
confidence intervals.
Usage
UDT(
case_a,
case_b,
controls_a,
controls_b,
sd_a = NULL,
sd_b = NULL,
sample_size = NULL,
r_ab = NULL,
alternative = c("two.sided", "greater", "less"),
conf_int = TRUE,
conf_level = 0.95,
conf_int_spec = 0.01,
na.rm = FALSE
)
Arguments
case_a |
Case's score on task A. |
case_b |
Case's score on task B. |
controls_a |
Controls' scores on task A. Takes either a vector of observations or a single value interpreted as mean. Note: you can supply a vector as input for task A while mean and SD for task B. |
controls_b |
Controls' scores on task B. Takes either a vector of observations or a single value interpreted as mean. Note: you can supply a vector as input for task B while mean and SD for task A. |
sd_a |
If single value for task A is given as input you must supply the standard deviation of the sample. |
sd_b |
If single value for task B is given as input you must supply the standard deviation of the sample. |
sample_size |
If A or B is given as mean and SD you must supply the sample size. If controls_a is given as vector and controls_b as mean and SD, sample_size must equal the number of observations in controls_a. |
r_ab |
If A and/or B is given as mean and SD you must supply the correlation between the tasks. |
alternative |
A character string specifying the alternative hypothesis,
must be one of |
conf_int |
Initiates a search algorithm for finding confidence
intervals. Defaults to |
conf_level |
Level of confidence for intervals, defaults to 95%. |
conf_int_spec |
The size of iterative steps for calculating confidence intervals. Smaller values gives more precise intervals but takes longer to calculate. Defaults to a specificity of 0.01. |
na.rm |
Remove |
Details
Running UDT
is equivalent to running TD
on discrepancy scores
making it possible to run unstandardised tests with covariates by applying
BTD_cov
to discrepancy scores.
Value
A list with class "htest"
containing the following components:
statistic | the t-statistic. |
parameter | the degrees of freedom for the t-statistic. |
p.value | the p-value of the test. |
estimate | unstandardised case scores, task difference and pont estimate of proportion control population expected to above or below the observed task difference. |
control.desc | named numerical with descriptive statistics of the control samples. |
null.value | the value of the difference under the null hypothesis. |
alternative | a character string describing the alternative hypothesis. |
method | a character string indicating what type of test was performed. |
data.name | a character string giving the name(s) of the data |
References
Crawford, J. R., & Garthwaite, P. H. (2005). Testing for Suspected Impairments and Dissociations in Single-Case Studies in Neuropsychology: Evaluation of Alternatives Using Monte Carlo Simulations and Revised Tests for Dissociations. Neuropsychology, 19(3), 318 - 331. doi:10.1037/0894-4105.19.3.318
Examples
UDT(-3.857, -1.875, controls_a = 0, controls_b = 0, sd_a = 1,
sd_b = 1, sample_size = 20, r_ab = 0.68)
UDT(case_a = size_weight_illusion[1, "V_SWI"], case_b = size_weight_illusion[1, "K_SWI"],
controls_a = size_weight_illusion[-1, "V_SWI"], controls_b = size_weight_illusion[-1, "K_SWI"])