reliability: Reliability function similar to the SPSS RELIABILITY command

In userfriendlyscience: Quantitative Analysis Made Accessible

Description

This function was developed to offer a function that roughly works similar to the SPSS RELIABILITY command.

Usage

reliability(data,
            items = NULL,
            itemDiagnostics = FALSE,
            digits = 2)

Arguments

data	The dataframe containing the variables (items, questions) of interest.
items	Optionally, the variables (items, questions) of interest. If omitted, all variables (items, questions) in the dataframe will be used.
itemDiagnostics	Whether to also display the item diagnostics (specifically, the corrected item-total correlation, mean and variance excluding each item, and the reliability coefficients excluding each item).
digits	The number of digits to use when displaying the results.

Author(s)

Gjalt-Jorn Peters

Maintainer: Gjalt-Jorn Peters <[e-mail]>

See Also

scaleStructure, the excellent psych package

Examples

## Not run: 
## (Not run to test because it takes a long time.)

data(testRetestSimData);
reliability(testRetestSimData[, 2:11], itemDiagnostics = TRUE);

## End(Not run)

Example output

Registered S3 method overwritten by 'GGally':
  method from   
  +.gg   ggplot2
Registered S3 methods overwritten by 'lme4':
  method                          from
  cooks.distance.influence.merMod car 
  influence.merMod                car 
  dfbeta.influence.merMod         car 
  dfbetas.influence.merMod        car 

Information about this analysis:

                 Dataframe: data
                     Items: t0_item1, t0_item2, t0_item3, t0_item4, t0_item5, t0_item6, t0_item7, t0_item8, t0_item9, t0_item10
              Observations: 250
     Positive correlations: 45 out of 45 (100%)

Estimates assuming interval level:

             Omega (total): 0.87
      Omega (hierarchical): 0.84
   Revelle's omega (total): 0.92
Greatest Lower Bound (GLB): 0.92
             Coefficient H: 0.9
          Cronbach's alpha: 0.85
Confidence intervals:
             Omega (total): [0.85, 0.9]
          Cronbach's alpha: [0.83, 0.87]

(Estimates assuming ordinal level not computed, as at least one item seems to have more than 8 levels; the highest number of distinct levels is 250 and the highest range is 99.58076. This last number needs to be lower than 9 for the polychoric function to work. If this is unexpected, you may want to check for outliers.)

Note: the normal point estimate and confidence interval for omega are based on the procedure suggested by Dunn, Baguley & Brunsden (2013) using the MBESS function ci.reliability, whereas the psych package point estimate was suggested in Revelle & Zinbarg (2008). See the help ('?scaleStructure') for more information.
Registered S3 methods overwritten by 'ufs':
  method                     from               
  grid.draw.ggProportionPlot userfriendlyscience
  pander.associationMatrix   userfriendlyscience
  pander.dataShape           userfriendlyscience
  pander.descr               userfriendlyscience
  pander.normalityAssessment userfriendlyscience
  print.CramersV             userfriendlyscience
  print.associationMatrix    userfriendlyscience
  print.confIntOmegaSq       userfriendlyscience
  print.confIntV             userfriendlyscience
  print.dataShape            userfriendlyscience
  print.descr                userfriendlyscience
  print.ggProportionPlot     userfriendlyscience
  print.meanConfInt          userfriendlyscience
  print.multiVarFreq         userfriendlyscience
  print.normalityAssessment  userfriendlyscience
  print.regrInfluential      userfriendlyscience
  print.scaleDiagnosis       userfriendlyscience
  print.scaleStructure       userfriendlyscience
  print.scatterMatrix        userfriendlyscience

Scale mean:     27.71
Scale variance: 13.45

Corrected item-total correlation and scale properties without each item:

          Item-total r Scale mean Scale var. Coeff. Alpha Omega  GLB Coeff. H
t0_item1          0.63         27         15         0.84  0.87 0.91     0.89
t0_item2          0.66         25         11         0.83  0.86 0.92     0.89
t0_item3          0.59         27         15         0.84  0.86 0.91     0.89
t0_item4          0.70         26         13         0.82  0.85 0.91     0.89
t0_item5          0.59         27         11         0.84  0.87 0.91     0.89
t0_item6          0.65         27         14         0.83  0.86 0.91     0.89
t0_item7          0.66         32         15         0.84  0.87 0.91     0.89
t0_item8          0.64         29         14         0.83  0.86 0.91     0.89
t0_item9          0.61         28         14         0.83  0.86 0.90     0.89
t0_item10         0.66         29         16         0.84  0.87 0.91     0.89

userfriendlyscience documentation built on May 2, 2019, 1:09 p.m.