Data collection is a science, not an art form. Be sure to use rigor and thought before assembling the data that you seek to analyze.

Ensuring Data Accuracy & Integrity

Be sure to address these point in your data collection plan. and make use of a data collection form.

  • Data should not be removed from a set without an appropriate statistical test or logic.
  • Generally, data should be recorded in time sequence.
  • Unnecessary rounding should be avoided.
    • If done, should be late in the process.
  • Screen the data to remove entry errors.
  • Avoid emotional bias.
  • Record measurements of items that change over time as quickly as possible after manufacture and again after the stabilization period.
  • Each important classification identification should be recorded alongside the data. (Ex. Time, machine, operator, gage, lab, material, conditions, etc).
  • Also see data sampling.

Coding Data

Sometimes it is more efficient to code data by adding, subtracting, multiplying or dividing by a factor.

Types of Data Coding

  • Substitution – ex. Replace 1/8ths of an inch with + / 1 deviations from center in integers.
  • Truncation– Ex. data set of 0.5541, 0.5542, 0.5547 – you might just remove the 0.554 portions.

Problems due to NOT Coding

  • practitioner tries to squeeze too many #s on a form – poor usability & legibility.
  • increased errors in data entry.
  • insensitivity of analytics due to rounding

Effects of Coding Data

  • Will affect the mean to the extent that the mean must be uncoded for reporting purposes.
  • Coding and uncoding of the mean will be exactly opposite. (Ex. Add X, subtract X or multiply by X, divide by X.)
  • The effect the coding has on standard deviation depends on how the data is coded.

Rounding Data

  • Rounding data will affect the standard deviation but not the mean – if done properly.

Also See:

Data Sampling

Data Collection Form

Data Collection Plan

Data Collection Reading List

Quality Control and Industrial Statistics. Fifth Edition A very good and comprehensive reviews of Acceptance Sampling, Control Chart and Statistics.

ASQ Six Sigma Black Belt Exam Data Collection Questions

Question: An important aspect of data collection is that the data collector should

(A) determine the dispersion of the data
(B) know how the data are to be used
(C) use a control chart to analyze the data
(D) use a stratified sampling plan


This section requires you to be logged in to either a Pass Your Six Sigma Exam or a free account. Sign up in seconds with the buttons below!

Login to your account
OR
Enroll in Pass Your Six Sigma Exam
OR
Get a Free Account

Questions, comments, issues, concerns? Please leave a note in the comments below!


This section requires you to be logged in.

Question: A method that changes data without significantly reducing accuracy or precision is known as

(A) bias adjustment
(B) statistical efficiency
(C) blocking
(D) coding

This section requires you to be logged in.

ASQ Six Sigma Green Belt Exam Data Collection Questions

Question: When the sampling method used creates a difference between the result obtained from the sample and the actual population value, the difference is known as

(A) correlation
(B) precision
(C) accuracy
(D) bias

This section requires you to be logged in.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.