Quality Measurement Techniques

[Tyme]

Sorry my first post is such a boring one but this is something I need to know.
I need to know what “quality measurement techniques” are and how they are used in the Quality Assurance field.
Thanks in advance to anyone who can tell me or direct me to more information about this topic.

[SmackFu]

Well, I guess summer’s officially over.

[sailor]

>> Well, I guess summer’s officially over

That depends on how you measure. While labor day may be the unofficial end, I believe the “official” end of summer is marked by the equinox. Better check your quality measurement technique next time

[Qadgop_the_Mercotan]

*Originally posted by Tyme *
**Sorry my first post is such a boring one but this is something I need to know.
I need to know what “quality measurement techniques” are and how they are used in the Quality Assurance field.
Thanks in advance to anyone who can tell me or direct me to more information about this topic. **

Well, every field has its own quality measurement techniques, from Hospital Management to Hydrodynamics. Try being a little more specific.

[Tyme]

Sorry, I should have been more specific.
I came across a job posting where the qualificatons required “familiarity of Quality Measurement Techniques”. Since this job posting is in the engineering field, I’m sure the required qualification means more than being able to read a Stanley tape measure.
Is there any Manufacturing/Mechanical engineers/technicians out there that have ever heard of this?

FYI, summer ends September 22, 2001

[Tyme]

To Qadgop:
I didn’t see your post before my last reply. It is for a company that manufactures products for the medical/biotech industries. (Plastic labware products).

[ultrafilter]

The quality measurement techniques I’ve seen rely on 95% confidence ellipses and other multivariate statistical techniques. Not exactly a tape measure, if I do say so myself.

[Qadgop_the_Mercotan]

*Originally posted by Tyme *
**To Qadgop:
I didn’t see your post before my last reply. It is for a company that manufactures products for the medical/biotech industries. (Plastic labware products). **

go google.com

type in “quality assurance” or “quality measurement techniques” along with medical or biotech/biotechnology.

see what you get.

[Squink]

Reviews of iso 9000 and cGMP (current good manufacturing practices) will get you started. There’s also cGLP (current good laboratory practices). Be aware that reading this material may cause your brain to go numb.

[Lance_Turbo]

*Originally posted by sailor *
That depends on how you measure. While labor day may be the unofficial end, I believe the “official” end of summer is marked by the equinox.

*Originally posted by Tyme *
FYI, summer ends September 22, 2001

Minor hijack, but I feel the need to squash this particular bit of ignorance whenever I see it.

Accrording to Cecil in this column.

There is a widespread misconception in this country–which extends, I might note, to the makers of most calendars, dictionaries, and encyclopedias–that summer “officially” starts on the day of the summer solstice, June 21 or 22, which is the longest day of the year. Americans also believe (1) that there is some valid scientific reason for doing it that way, and (2) that everybody in the Northern Hemisphere does it that way, and always has.

None of these things is true. So far as I have been able to discover, no scientific or governmental body has ever formally declared that summer starts on the solstice.

and

He notes that meteorologists define summer simply as June, July, and August. “For practical purposes, the meteorological definition is the best one, being very closely to the [weather] statistics,” he says.

In fact, it appears that June 1 was accepted as the beginning of summer in the United States until relatively recently.

Welcome to autumn.

[sailor]

If there is no “official” definition of summer then, the only definition we have is what most people consider it to be and, as you have said, it is mostly between the solstice and the equinox. Britannica says: “it is usually defined as the period between the summer solstice and the autumnal equinox”. The US Naval Observatory concurs as do most other sources. The only thing I have seen is a differentiation between astronomical seasons and meteorological seasons but, in my experience, when people refer to simply seasons, with no qualifier, then they refer to astronomical seasons as defined by Britannica.

[Lance_Turbo]

are you disagreeing with Cecil?

[Koxinga]

*Originally posted by Tyme *
**Sorry my first post is such a boring one but this is something I need to know.
I need to know what “quality measurement techniques” are and how they are used in the Quality Assurance field.
Thanks in advance to anyone who can tell me or direct me to more information about this topic. **

Some basic tools for quality measurement include Pareto diagrams, cause-and-effect (AKA “fishbone”) diagrams, and control charts. The latter–control charts–will introduce you to a whole subfield within quality assurance called “statistical process control”, or SPC. Try looking up some of those terms and tell me if it puts you on track, or if you have something else in mind.

Could you tell us what you need this info for?

[sailor]

>> are you disagreeing with Cecil?

It could very well be true and yet never have happened.

[Crafter_Man]

I’m an EE and work in an Electronics Design Lab, so I can only tell you what it means in the context of my work. (But this might be accurate, given that the ad mentioned engineering.)

Understanding “Quality Measurement Techniques” basically means you have an understanding of metrology principles. Metrology, if you’re not aware, is “the science of physical measurements,” and deals with the “what, when, where, how, and why” of scientific measurements.

Off the top of my head, I came up the following mini-quiz. If you can answer half of these, then you would have no problem claiming you understand “Quality Measurement Techniques.”

• Do you know what “NIST” stands for, and what it is?
• Do you know what a “standard” is? Do you know what a “DUT” or “UUT” is?
• Do you understand the concept of “traceability”?
• Do you know what the “4:1 tolerance rule” is?
• Do you know what a “calibration interval” is?
• Do you know the difference between a “comparison calibration” and “calibration using an intrinsic standard”?
• Do you know the difference between “absolute error” and “relative error”?
• Do you know how to calculate mean and standard deviation of a finite number if data points? Do you understand what these values represent?
• Do you know how to calculate measurement uncertainty based on calibration data?
• Do you know what “3-sigma” means?
• Define the following: adjustment, calibration, certification. What are their differences?
• Do you know what “as-found” data is? Do you know what “as-left” data is?
• Do you understand what environmental conditions can cause measurement errors?
• Do you understand the difference between accuracy, precision, tolerance, and uncertainty?
• Do you know what “repeatability” is?
• Do you know what “reproducibility” is?
• Can you define the following terms: bias, offset, gain, “zero”, range, full-scale, drift, noise, and linearity?
• Do you understand resolution and readability?
• Do you know the difference between “systematic error” and “random error”?
• Do you understand “measurement assurance” concepts?
• Do you know what a “least squares fit” is, and when/why it is used?
• Do you understand curve-fitting techniques such as polynomial, logarithmic, and piece-wise linear?

The above can be applied to any measurement. There are also application-specific questions, such as:

• Do you know how to properly ring a gage block?
• Do you know how to perform a temperature-compensated dimensional measurement?
• Do you know what external conditions can create errors in a voltmeter?
• Do you know how to digitize an analog signal? Do you know how to calculate measurement resolution of an A/D converter?
• Do you know under what circumstances excessive lead-lengths (wires) can cause a measurement error?

You get the picture.

I’m not listing these questions to “demonstrate how much I know” about this subject; I just consider myself “somewhat knowledgeable” (i.e. I know enough to be dangerous). I’m simply giving you a flavor of what they might be looking for. If this is what they’re looking for, and if you do not understand these concepts, do not try to B.S. them - they’ll figure out soon enough that you lack this experience, and the consequences will be ugly. Instead, be honest with them: tell them you understand the importance of metrology, and you’re eager to learn about this science.

[Tyme]

Thanks. This seems to be the info I need. Since I don’t know the answers to any of the questions you listed, it looks like I’ve got alot of studying to do. I’ll see if I can find any good books about metrology.

[Crafter_Man]

*Originally posted by Tyme *
**Thanks. This seems to be the info I need. Since I don’t know the answers to any of the questions you listed, it looks like I’ve got alot of studying to do. I’ll see if I can find any good books about metrology. **

You’re correct, if this is what they’re looking for.

If you want to learn more about metrology principles, drop me a line. (Press the “profile” link at the end of this post for my email address.) I’m certainly not an expert in the field, but I can help you with the basics. I can also provide some names of good reference materials.