What Control Chart should be used for Microbial Limit (NMT 100 cfu/m3)

J

jihyunpark

#1
Dear All,

Kindly give me an advice what control chart i should use for testing date of microbiologic count limit (Specification is NMT 100 cfu/m3). Furthermore, please also give me a template of that chart if you have.

Thanks.
 
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Darius

Quite Involved in Discussions
#3
The problem with microbial counts is that in many cases the count is "CERO" (more that 70% of data points), or no detection and it can be some very near to "0", but if something happen, it can grow a lot.

:2cents:If this is the case I couldn't recommend SPC:nope: (unless u-chart as steve said), precontrol could be the tool.

If we can see the data (an example) can be enlighting to us, and direct our advices to your variable's behabiour.
 
Last edited:

Bev D

Heretical Statistician
Staff member
Super Moderator
#4
It is impossible to advise you on exactly which chart you should use without seeing your data. I have numerous charts for microbial growth in my organization but they are not all the same chart type as the 'processes' are different. With different processes you get different behavior and so you must use differetn chart types.
 
G

glarson

#6
I hope I'm not stepping on any toes.

I guess I'm too new. They won't let me post links.
I'll post this once without the links then again with, when my post count is greater 4. <ugh>
I came across this pdf a some time ago.
<link omitted>

I used the example in this pdf to create spc charts for a micro lab. Most of my charts' y axes started at 0. I used Shewhart individuals control charts, With one exception: no LCL. It was assumed that results less than the detection level was = 0. In a few cases that involved a large cfu range (like 50 - 10000 for example) I converted the data to a logarithmic scale. This was not ideal and the only big benefit may have been that the charts looked more aesthetically pleasing. In your case, though, I do not think you need to bother with logarithms.


I noticed that you have some results that are lower than your detection limit of 10. ??


If you do not have the calculations you can find them on wiki:
<link omitted>

I no longer have any examples to show, since I am no longer with the company that I created those charts for; most of my SPC work was in MS Access anyway.
GL
 
G

glarson

#7
Now lets try it...

I came across this pdf a some time ago. http://www.fsis.usda.gov/PDF/FAQs_SPC_1.pdf

I used the example in this pdf to create spc charts for a micro lab. Most of my charts y axis started at 0. I used Shewhart individuals control charts, With one exception: no LCL. It was assumed that results less than the detection level was = 0. In a few cases that involved a large cfu range (like 50 - 10000 for example) I converted the data to a logarithmic scale. This was not ideal and the only big benefit may have been that the charts looked more aesthetically pleasing. In your case, though, I do not think you need to bother with logarithms.


I noticed that you have some results that are lower than your detection limit of 10. ??


If you do not have the calculations you can find them on wiki:
http://en.wikipedia.org/wiki/Shewhart_individuals_control_chart

I no longer have any examples to show, since I am no longer with the company that I created those charts for; most of my SPC work was in MS Access anyway.
GL
 

Stijloor

Staff member
Super Moderator
#8
<snip> I guess I'm too new. They won't let me post links.
Actually, "They" is Mr. Marc Smith, the owner and host of this site.

I'll post this once without the links then again with, when my post count is greater 4. <ugh>
Yes, you are correct, that provision is implemented to prevent link spammers from contaminating our Forums. (The required post count is 5; certain forum posts do not count).

Hope this clarifies. ;)

Stijloor, Forum Moderator.
 
S

siju234

#10
Dear all,


Can any body clarify my following doubts regarding microbiology lab?


1, What is the need of Air condition in microlab? whether the air condition should be on round the clock?
2,How we can identify classify the class of my microlab?


Thanks in Advance,
sijo joseph
INDIA
 
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