test2norm: Convert raw neuropsychological test scores to demographically...

In test2norm: Normative Standards for Cognitive Tests

Convert raw neuropsychological test scores to demographically adjusted norms.

Description

Convert raw neuropsychological test scores to demographically adjusted norms.

Usage

test2norm(
  data = NULL,
  test = NULL,
  test.min = NULL,
  test.max = NULL,
  test.better = c("High", "Low"),
  group.id = NULL,
  control.id = NULL,
  all.controls = FALSE,
  demographics = NULL,
  mfp.alpha = 1,
  rnd.s = FALSE,
  rnd.a = FALSE,
  mean.a = 50,
  sd.a = 10
)

Arguments

data	a data frame containing the variables needed for the norming process
test	a character string specifying the name of the test to be normed
test.min	a real number indicating the smallest possible test score
test.max	a real number indicating the largest possible test score
test.better	a character string indicating direction of the scores. Use "High" if high test scores imply better performance, use "Low" otherwise.
group.id	a character string specifying the name of the variable containing group identification (i.e. control vs exposed/test/risk). Ignored, if all.controls = TRUE.
control.id	a character string specifying the label of the control group within group.id variable. Ignored, if all.controls = TRUE.
all.controls	a logical indicating whether all observations should be treated as controls. Overwrites group.id and control.id.
demographics	a single or multiple character strings (concatenated by c() function) specifying the names of demographic predictors to be included into normative formulas.
mfp.alpha	a numeric value between 0 and 1 that sets significance level for inclusion of demographic predictors into normative formula. Passed to the mfp() function. Default value is 1 for inclusion of all predictors regardless of their significance.
rnd.s	a logical indicating whether the scaled scores should be rounded. Default is FALSE.
rnd.a	a logical indicating whether the adjusted scores (T-scores) should be rounded. Default is FALSE.
mean.a	numeric value for the mean of adjusted score (T-score) distribution.
sd.a	numeric value for the standard deviation of adjusted score (T-score) distribution.

Details

The test2norm() function can be used by neuropsychologists, who wish to construct normative formulas for cognitive tests that adjust for expected effects of demographic characteristics (e.g., age), using methods described in Heaton et al. (2003 & 2009). The norming procedure makes use of the mfp() function from the mfp package to explore nonlinear associations between cognition and demographic variables. The raw test scores that have many decimal digits should be rounded to fewer digits prior to the application of the test2norm() function. This will significantly reduce software running time. The recommended number of decimal digits is 4 or fewer. Detailed description of the procedure will be found in Umlauf et al (2022).

Value

A list consisting of 6 objects. The first four are vectors containing the original raw test scores and the calculated scaled scores, demographically adjusted scores, and deficit scores. The fifth object in the list, called SS.maps, contains conversions from raw scores to scaled scores in a form of a table with two columns, one representing scaled scores (one per row) and one representing raw scores (range of raw values corresponding to each scaled score). The last item in the output list is also a list called MFP.formulas and contains the information for calculation of adjusted scores, including variable transformations (if any), multiple fractional polynomial (MFP) model coefficients, and the standard deviation of residuals resulting from the MFP modeling.

Author(s)

Anya Umlauf

References

Umlauf A et al. (2022) Automated procedure for demographic adjustments on cognitive test scores. Manuscript submitted for publication.

Heaton RK, Taylor MJ, & Manly J (2003) Demographic effects and use of demographically corrected norms with the WAIS-III and WMS-III. In: Tulsky D et al. (Eds.) Clinical Interpretation of the WAIS-III and WMS-III. San Diego, CA: Academic Press, 183-210.

Heaton RK, Ryan L, & Grant I (2009) Demographic influences and use of demographically corrected norms in neuropsychological assessment. In Grant I & Adams KM (Eds.) Neuropsychological Assessment of Neuropsychiatric and Neuromedical Disorders. New York, NY: Oxford University Press, 127-155.

Benner A (2005) mfp: Multivariable fractional polynomials. R News 5(2): 20–23.

Examples

data(PsychTestData)
test2norm(data = PsychTestData, test = "rawscore",
          test.min = 0, test.max = 36, test.better = "High",
          group.id = "group", control.id = "control",
          demographics = c("age", "sex"))

test2norm documentation built on March 18, 2022, 6:31 p.m.