THE VITAMIN B12 AND FOLATE PATHOLOGY INVESTIGATION
THE INVESTIGATION OF ERRORS IN PATHOLOGY TESTS
FOR VITAMIN B12 AND FOLATE DEFICIENCY
BY MEANS OF MEDICAL EXPERIMENTS
THE METHYLMALONIC ACID INVESTIGATION
THE MMA EXPERIMENT
Summary
Method
Analysis - Pxu
Observations
Results - Notes
Results - Series 1
Conclusions

Derivation of Probability pxu

Source: http://mathworld.wolfram.com/ConfidenceInterval.html, reference AB30

Assuming Normal Distribution of results:

Pxu = ERF(n/SQRT(2))

where

  • Pxu = probability result x lies within ± n SD of mean u in figure A
  • ERF = error function
  • n = specified number of Standard Deviations
  • SD = Standard Deviation

Substituting #SD for n and taking absolute value of # SD:

Pxu = ERFC(ABS(#SD)/(SQRT(2)))

where

  • Pxu = probability each independent result lies within # SD of either side of mean = either half of area under curve in figure B
  • # SD = measured difference between any result and the mean

Taking complement of error function to select area outside of confidence interval:

pxu = ERFC(ABS(#SD)/(SQRT(2)))

where

  • pxu = probability any result lies outside # SD of either side of mean = either half of area under curve in figure C
  • ERFC = complimentary error function = 1 - ERF

pxu = ERFC(ABS(#SD)/(SQRT(2)))

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