Use critical values helpers with t-value

ehmicky · Oct 31, 2021 · 2a0cf49 · 2a0cf49
1 parent 9a88e1d
commit 2a0cf49
Show file tree

Hide file tree

Showing 2 changed files with 226 additions and 37 deletions.
diff --git a/src/stats/critical_values/map.js b/src/stats/critical_values/map.js
@@ -40,8 +40,8 @@ const normalizeKey = function ([key, value]) {
 
 // Retrieve the last entry which can used as `preciseMap`
 const isLastPreciseKey = function ([key], index, entries) {
-  const [nextKey] = entries[index + 1]
-  return key !== nextKey - 1
+  const nextEntry = entries[index + 1]
+  return nextEntry === undefined || key !== nextEntry[0] - 1
 }
 
 // Retrieve a critical value given a specific degrees of freedom and

diff --git a/src/stats/critical_values/student_t.js b/src/stats/critical_values/student_t.js
@@ -1,40 +1,229 @@
-// Retrieve t-value, using t-distribution, two-tailed, with 95% significance
-// level.
-export const getStudentTValue = function (degreesOfFreedom) {
-  if (degreesOfFreedom >= T_VALUES.length) {
-    return MIN_T_VALUE
-  }
+/* eslint-disable max-lines */
+import { getCriticalValue, getCriticalValuesMap } from './map.js'
 
-  return T_VALUES[degreesOfFreedom - 1]
+// Retrieve t-value, using t-distribution, two-tailed
+export const getStudentTValue = function (degreesOfFreedom) {
+  const singleSignificanteRate = (1 + SIGNIFICANCE_RATE) / 2
+  return getCriticalValue(
+    STUDENT_T_MAP,
+    degreesOfFreedom,
+    singleSignificanteRate,
+  )
 }
 
-const MIN_T_VALUE = 1.96
+const SIGNIFICANCE_RATE = 0.95
 
-// We hardcode first t-values because computing them is quite complex.
-// Beyond a specific size, they converge to `MIN_T_VALUE` with a very minor
-// difference.
-/* eslint-disable no-magic-numbers */
-const T_VALUES = [
-  12.7065, 4.3026, 3.1824, 2.7764, 2.5706, 2.4469, 2.3646, 2.306, 2.2621,
-  2.2282, 2.201, 2.1788, 2.1604, 2.1448, 2.1314, 2.1199, 2.1098, 2.1009, 2.093,
-  2.086, 2.0796, 2.0739, 2.0686, 2.0639, 2.0596, 2.0555, 2.0518, 2.0484, 2.0452,
-  2.0423, 2.0395, 2.0369, 2.0345, 2.0322, 2.0301, 2.0281, 2.0262, 2.0244,
-  2.0227, 2.0211, 2.0196, 2.0181, 2.0167, 2.0154, 2.0141, 2.0129, 2.0117,
-  2.0106, 2.0096, 2.0086, 2.0076, 2.0066, 2.0057, 2.0049, 2.0041, 2.0032,
-  2.0025, 2.0017, 2.001, 2.0003, 1.9996, 1.999, 1.9983, 1.9977, 1.9971, 1.9966,
-  1.996, 1.9955, 1.995, 1.9944, 1.9939, 1.9935, 1.993, 1.9925, 1.9921, 1.9917,
-  1.9913, 1.9909, 1.9904, 1.9901, 1.9897, 1.9893, 1.9889, 1.9886, 1.9883,
-  1.9879, 1.9876, 1.9873, 1.987, 1.9867, 1.9864, 1.9861, 1.9858, 1.9855, 1.9852,
-  1.985, 1.9847, 1.9845, 1.9842, 1.984, 1.9837, 1.9835, 1.9833, 1.983, 1.9828,
-  1.9826, 1.9824, 1.9822, 1.982, 1.9818, 1.9816, 1.9814, 1.9812, 1.981, 1.9808,
-  1.9806, 1.9805, 1.9803, 1.9801, 1.9799, 1.9798, 1.9796, 1.9794, 1.9793,
-  1.9791, 1.979, 1.9788, 1.9787, 1.9785, 1.9784, 1.9782, 1.9781, 1.9779, 1.9778,
-  1.9777, 1.9776, 1.9774, 1.9773, 1.9772, 1.9771, 1.9769, 1.9768, 1.9767,
-  1.9766, 1.9765, 1.9764, 1.9762, 1.9761, 1.976, 1.9759, 1.9758, 1.9757, 1.9756,
-  1.9755, 1.9754, 1.9753, 1.9752, 1.9751, 1.975, 1.9749, 1.9748, 1.9747, 1.9746,
-  1.9745, 1.9744, 1.9744, 1.9743, 1.9742, 1.9741, 1.974, 1.9739, 1.9739, 1.9738,
-  1.9737, 1.9736, 1.9735, 1.9735, 1.9734, 1.9733, 1.9732, 1.9731, 1.9731, 1.973,
-  1.9729, 1.9729, 1.9728, 1.9727, 1.9727, 1.9726, 1.9725, 1.9725, 1.9724,
-  1.9723, 1.9723, 1.9722, 1.9721, 1.9721, 1.972, 1.972, 1.9719,
+const STUDENT_T_RAW = [
+  {
+    significanceRate: 0.975,
+    getMaxValue() {
+      return MAX_T_VALUE
+    },
+    criticalValues: {
+      1: 12.7065,
+      2: 4.3026,
+      3: 3.1824,
+      4: 2.7764,
+      5: 2.5706,
+      6: 2.4469,
+      7: 2.3646,
+      8: 2.306,
+      9: 2.2621,
+      10: 2.2282,
+      11: 2.201,
+      12: 2.1788,
+      13: 2.1604,
+      14: 2.1448,
+      15: 2.1314,
+      16: 2.1199,
+      17: 2.1098,
+      18: 2.1009,
+      19: 2.093,
+      20: 2.086,
+      21: 2.0796,
+      22: 2.0739,
+      23: 2.0686,
+      24: 2.0639,
+      25: 2.0596,
+      26: 2.0555,
+      27: 2.0518,
+      28: 2.0484,
+      29: 2.0452,
+      30: 2.0423,
+      31: 2.0395,
+      32: 2.0369,
+      33: 2.0345,
+      34: 2.0322,
+      35: 2.0301,
+      36: 2.0281,
+      37: 2.0262,
+      38: 2.0244,
+      39: 2.0227,
+      40: 2.0211,
+      41: 2.0196,
+      42: 2.0181,
+      43: 2.0167,
+      44: 2.0154,
+      45: 2.0141,
+      46: 2.0129,
+      47: 2.0117,
+      48: 2.0106,
+      49: 2.0096,
+      50: 2.0086,
+      51: 2.0076,
+      52: 2.0066,
+      53: 2.0057,
+      54: 2.0049,
+      55: 2.0041,
+      56: 2.0032,
+      57: 2.0025,
+      58: 2.0017,
+      59: 2.001,
+      60: 2.0003,
+      61: 1.9996,
+      62: 1.999,
+      63: 1.9983,
+      64: 1.9977,
+      65: 1.9971,
+      66: 1.9966,
+      67: 1.996,
+      68: 1.9955,
+      69: 1.995,
+      70: 1.9944,
+      71: 1.9939,
+      72: 1.9935,
+      73: 1.993,
+      74: 1.9925,
+      75: 1.9921,
+      76: 1.9917,
+      77: 1.9913,
+      78: 1.9909,
+      79: 1.9904,
+      80: 1.9901,
+      81: 1.9897,
+      82: 1.9893,
+      83: 1.9889,
+      84: 1.9886,
+      85: 1.9883,
+      86: 1.9879,
+      87: 1.9876,
+      88: 1.9873,
+      89: 1.987,
+      90: 1.9867,
+      91: 1.9864,
+      92: 1.9861,
+      93: 1.9858,
+      94: 1.9855,
+      95: 1.9852,
+      96: 1.985,
+      97: 1.9847,
+      98: 1.9845,
+      99: 1.9842,
+      100: 1.984,
+      101: 1.9837,
+      102: 1.9835,
+      103: 1.9833,
+      104: 1.983,
+      105: 1.9828,
+      106: 1.9826,
+      107: 1.9824,
+      108: 1.9822,
+      109: 1.982,
+      110: 1.9818,
+      111: 1.9816,
+      112: 1.9814,
+      113: 1.9812,
+      114: 1.981,
+      115: 1.9808,
+      116: 1.9806,
+      117: 1.9805,
+      118: 1.9803,
+      119: 1.9801,
+      120: 1.9799,
+      121: 1.9798,
+      122: 1.9796,
+      123: 1.9794,
+      124: 1.9793,
+      125: 1.9791,
+      126: 1.979,
+      127: 1.9788,
+      128: 1.9787,
+      129: 1.9785,
+      130: 1.9784,
+      131: 1.9782,
+      132: 1.9781,
+      133: 1.9779,
+      134: 1.9778,
+      135: 1.9777,
+      136: 1.9776,
+      137: 1.9774,
+      138: 1.9773,
+      139: 1.9772,
+      140: 1.9771,
+      141: 1.9769,
+      142: 1.9768,
+      143: 1.9767,
+      144: 1.9766,
+      145: 1.9765,
+      146: 1.9764,
+      147: 1.9762,
+      148: 1.9761,
+      149: 1.976,
+      150: 1.9759,
+      151: 1.9758,
+      152: 1.9757,
+      153: 1.9756,
+      154: 1.9755,
+      155: 1.9754,
+      156: 1.9753,
+      157: 1.9752,
+      158: 1.9751,
+      159: 1.975,
+      160: 1.9749,
+      161: 1.9748,
+      162: 1.9747,
+      163: 1.9746,
+      164: 1.9745,
+      165: 1.9744,
+      166: 1.9744,
+      167: 1.9743,
+      168: 1.9742,
+      169: 1.9741,
+      170: 1.974,
+      171: 1.9739,
+      172: 1.9739,
+      173: 1.9738,
+      174: 1.9737,
+      175: 1.9736,
+      176: 1.9735,
+      177: 1.9735,
+      178: 1.9734,
+      179: 1.9733,
+      180: 1.9732,
+      181: 1.9731,
+      182: 1.9731,
+      183: 1.973,
+      184: 1.9729,
+      185: 1.9729,
+      186: 1.9728,
+      187: 1.9727,
+      188: 1.9727,
+      189: 1.9726,
+      190: 1.9725,
+      191: 1.9725,
+      192: 1.9724,
+      193: 1.9723,
+      194: 1.9723,
+      195: 1.9722,
+      196: 1.9721,
+      197: 1.9721,
+      198: 1.972,
+      199: 1.972,
+      200: 1.9719,
+    },
+  },
 ]
-/* eslint-enable no-magic-numbers */
+
+const MAX_T_VALUE = 1.96
+const STUDENT_T_MAP = getCriticalValuesMap(STUDENT_T_RAW)
+/* eslint-enable max-lines */