Parameters:
(1) lower limit of reference range
(2) upper limit of reference range
(3) statistical limits to the reference range (95%, 97.5%, 98.8%, 99%)
upper limit =
= (mean) + ((number of standard deviations) * (standard deviation))
lower limit =
= (mean) - ((number of standard deviations) * (standard deviation))
mean value for the normal reference range =
= (lower limit) + (((upper limit) - (lower limit)) / 2) =
= ((upper limit) + (lower limit)) / 2
standard deviation =
= (((upper limit) - (lower limit)) / 2) / (number of standard deviations in the reference range) =
= ((upper limit) - (lower limit)) / (2 * (number of standard deviations))
|
Limits for the Reference Range
|
Number of Standard Deviations
|
|
68.27%
|
1
|
|
95.45%
|
2
|
|
97.5%
|
2.25
|
|
98.8%
|
2.5
|
|
99.73%
|
3
|
