
218 Part II The Step-by-Step Guide to the TIQM Quality System
Table 5-9: Example Calculation of the Standard Deviation of a Sample
6
STANDARD DEVIATION
CALCULATION STEPS
CALCULATION RESULT
1. Count the number of records in the
sample.
50 = 50
2. Count the number of data elements
in all records that contain a defect of
the IQ Characteristic measured.
23 = 23
3. Calculate the Mean (x) or average
number of errors per record by divid-
ing the total number of errors by the
number of sampled records.
23 / 50 = 0.46
4. Calculate the Deviation (d) of each
record by subtracting the Mean num-
ber of errors from the actual number
of errors in the record.
Record 1 = 0 - 0.46 =
Record 2 = 1 - 0.46 =
etc.
-0.46
0.54
5. Calculate the Deviation Squared (d
2
)
for each record by multiplying the
deviation by itself.
Rec 1 = -0.46 x -0.46=
Rec 2 = 0.54 x 0.54 =
etc.
0. 2116
0.2916
6. Calculate the Sum of the Deviations
Squared (Σd
2
) by adding all of the
deviat