4. Root Mean Square 
Using previous definitions, the root mean square (RMS) was 
derived by: 
RMS = Recta fa fe EWEN 1 
This value provides an indication of the degree of scattering or 
dispersion of the residuals about their mean. 
5. Median 
The median of the residuals was computed next and is an 
average that divides a distribution into two equal parts in terms 
| , of the 
of frequencies. It is the value that leaves 50%, ( 5 
number of residuals above and below it. The formula used for 
obtaining this value is: 
W 
Median = L +(*) | 
Where 
: N 
L = upper boundary value of interval where >) occurs or 
is as close as possible without exceeding it 
; a IN 
W = number of values needed from next interval to obtain > 
f = total number of values in next interval 
range of magnitude of the interval (in this case, 0.5°) 
6. 80 Percent Confidence Interval 
Finally, an 80% confidence interval (80 PCT CONF) for the 
median was computed by the following formula: 
80 PCT CONF = Median +1.28 (Standard Error of the Median) 
