Matthew W Ford
Northern Kentucky University College of Business

 

 

Courses:
MGT 305
MGT 307
MGT 415
MGT 490
FIN 450

Research

 

Student
Resources:
Memos
ModelMemos
Resumes
% Diff
Tables
Graphs
Citations
QC .xls
QCformulas
 

Home

QC Formulas and Factors (Updated 02/24/2007 06:43 PM)

Control Charts

a) Variables data, two or more observations per sample

x-bar chart:

   

r-bar chart:

b) Variables data; one observation per sample

x chart:

   

r chart:

   

Note:  r-bar found by finding the average of moving ranges between samples.

c) Attributes data; counted data (c-chart)

  

d) Attributes data; percentage data (p-chart)

    

Process Capability Index

Factors For Control Charts and Process Capability

n

A2

d2

D3

D4

2 1.180 1.128 0 3.267
3 1.023 1.693 0 2.574
4 0.729 2.059 0 2.282
5 0.577 2.326 0 2.114
6 0.483 2.534 0 2.004
7 0.419 2.704 0.076 1.924
8 0.373 2.847 0.136 1.864
9 0.337 2.970 0.184 1.816
10 0.308 3.078 0.223 1.777
11 0.285 3.173 0.256 1.744
12 0.266 3.258 0.283 1.717
13 0.249 3.336 0.307 1.693
14 0.235 3.407 0.328 1.672
15 0.223 3.472 0.347 1.653
16 0.212 3.532 0.363 1.637
17 0.203 3.588 0.378 1.622
18 0.194 3.640 0.391 1.608
19 0.187 3.689 0.403 1.597
20 0.180 3.735 0.415 1.585

Adapted from ASTM STP 15D ASTM Manual on presentation of data and control chart analysis. Philadelphia: American Society for Testing and Materials.

 

Site maintained 1999-2016 by Matthew W. Ford.