Farnsworth-Munsell Statistics

Evaluation of poor performance and asymmetry in the Farnsworth-Munsell 100-hue test

Jonathan D. Victor

Invest. Ophth. Vis. Sci. 29, 476-481 (1988)

Abstract

A statistical method for the analysis of errors on the Farnsworth-Munsell 100-hue test is introduced. The extent of asymmetry of errors are summarized by two indices, I1 and I2, derived from Fourier analysis of the error scores for the individual caps. The second index, I2, describes the (bipolar) color axis; the first index, I1, describes (monopolar) asymmetry of performance. The present analysis differs from previous approaches based on Fourier analyis of the errors in two ways. (1) A procedure is introduced which corrects the indices I1 and I2 for the biases that result from the segmentation of the test into four boxes. (2) Statistics for the significance of I1 and I2 are derived by a Monte Carlo procedure, which properly handles the complex interdependence of individual error scores for each cap.


Table 1: Parameters of the distribution of total error for incompletely-randomized arrangements of the Farnsworth-Munsell caps

Cap arrangements are generated by applying pairwise swaps of adjacent caps. The statistics for each average number of swaps per tray (f) are calculated from 10000 independent arrangements. The statistics for the last line of the table (infinite number of swaps per tray) were calculated from 10000 completely random cap arrangements. s.d., standard deviation; c.v., coefficient of variation (s.d./mean).

swaps/  mean  s.d. c.v.  ..................critical values....................
 tray   total            0.001 0.010 0.025 0.050 0.500 0.950 0.975 0.990 0.999
 (f)    error

    1   15.2  7.4  0.491    0     0     4     4    16    29    33    37    45
    2   29.3 10.1  0.346    4     8    12    12    28    49    53    57    65
    4   54.0 13.3  0.247   20    24    28    32    52    77    81    89   101
    6   75.7 15.6  0.207   32    40    48    52    76   105   109   117   133
   10  112.2 19.3  0.172   56    68    76    80   112   145   153   161   177
   20  181.5 26.2  0.145  108   124   132   140   180   225   237   245   269
   40  277.0 35.8  0.129  176   196   208   220   276   337   353   369   397
   60  348.2 43.0  0.124  228   256   268   280   348   425   437   457   493
  100  454.3 53.5  0.118  304   340   356   372   452   549   569   589   645
  200  633.2 68.7  0.109  432   484   504   524   632   753   773   805   869
  300  749.7 79.6  0.106  512   576   600   624   748   832   913   945  1013
  400  834.6 84.4  0.101  592   644   672   700   832   977  1005  1037  1093
  600  952.4 91.3  0.096  696   740   776   804   952  1105  1133  1173  1237
 1000 1085.2 93.1  0.086  792   872   904   936  1084  1241  1269  1305  1373
 1500 1151.1 88.9  0.077  876   940   976  1004  1152  1297  1321  1353  1425
 inf. 1204.2 84.7  0.070  948  1004  1036  1060  1208  1341  1369  1397  1465

Table 2: Critical values of the distribution of the amplitude of the first and second harmonic indices |I1| and |I2|

|I1| and |I2| are the ratio of the first and second Fourier components of the error scores to the zeroth Fourier component. The statistics for each degree of randomization are calculated from 10000 independent arrangements, as in Table 1. Harmonic indices are measured with or without the correction for finite boxes.

(corrected for finite boxes)
 mean   swaps/   .................critical values..................
 total   tray       first harmonic             second harmonic
 error   (f)     0.500 0.950 0.990 0.999    0.500 0.950 0.990 0.999

  15.2     1     0.450 0.997 0.997 0.997    0.439 0.987 0.987 0.987
  29.3     2     0.304 0.693 0.914 0.997    0.300 0.699 0.899 0.987
  54.0     4     0.213 0.464 0.590 0.749    0.208 0.460 0.583 0.742
  75.7     6     0.177 0.377 0.477 0.624    0.174 0.377 0.484 0.606
 112.2    10     0.148 0.311 0.391 0.484    0.143 0.303 0.385 0.485
 181.5    20     0.122 0.255 0.312 0.380    0.116 0.248 0.317 0.415
 277.0    40     0.108 0.224 0.270 0.327    0.098 0.215 0.268 0.342
 348.2    60     0.101 0.211 0.263 0.322    0.088 0.196 0.251 0.310
 454.3   100     0.092 0.194 0.239 0.305    0.078 0.176 0.226 0.281
 633.2   200     0.083 0.174 0.214 0.264    0.062 0.146 0.187 0.237
 749.7   300     0.076 0.159 0.198 0.238    0.055 0.130 0.170 0.225
 834.6   400     0.072 0.154 0.190 0.236    0.050 0.120 0.156 0.198
 952.4   600     0.065 0.136 0.172 0.207    0.044 0.109 0.144 0.183
1085.2  1000     0.057 0.121 0.151 0.187    0.042 0.098 0.128 0.162
1151.1  1500     0.052 0.112 0.141 0.171    0.042 0.094 0.121 0.157
1204.2  inf.     0.048 0.101 0.128 0.166    0.045 0.097 0.124 0.152

(uncorrected for finite boxes)
 mean   swaps/   .................critical values..................
 total   tray       first harmonic             second harmonic
 error   (f)     0.500 0.950 0.990 0.999    0.500 0.950 0.990 0.999

  15.2     1     0.439 0.997 0.997 0.997    0.435 0.987 0.987 0.987
  29.3     2     0.299 0.685 0.913 0.997    0.298 0.680 0.895 0.987
  54.0     4     0.208 0.455 0.586 0.740    0.207 0.450 0.566 0.708
  75.7     6     0.175 0.374 0.468 0.619    0.174 0.367 0.471 0.590
 112.2    10     0.144 0.304 0.385 0.469    0.143 0.297 0.366 0.460
 181.5    20     0.120 0.249 0.308 0.370    0.116 0.241 0.300 0.377
 277.0    40     0.105 0.220 0.268 0.329    0.099 0.207 0.257 0.313
 348.2    60     0.099 0.208 0.257 0.306    0.090 0.190 0.233 0.282
 454.3   100     0.093 0.192 0.238 0.298    0.080 0.171 0.212 0.265
 633.2   200     0.084 0.176 0.215 0.260    0.064 0.140 0.178 0.220
 749.7   300     0.078 0.164 0.201 0.243    0.057 0.125 0.157 0.207
 834.6   400     0.075 0.157 0.195 0.242    0.052 0.115 0.147 0.182
 952.4   600     0.068 0.143 0.178 0.218    0.045 0.104 0.134 0.170
1085.2  1000     0.059 0.126 0.155 0.192    0.041 0.093 0.118 0.151
1151.1  1500     0.054 0.115 0.147 0.177    0.041 0.090 0.115 0.145
1204.2  inf.     0.049 0.105 0.132 0.164    0.043 0.093 0.116 0.143


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