CONTROL CHART BASICS and the X-BAR AND R CHART +++++ EXAMPLE

The control chart basics, including the 2 types of variation and how we distinguish between common and special cause variation, along with how to create a rational subgroup!
We also cover the equations and constants for the X-bar and R (Range) chart, and work an example of this important control chart.
0:00 - Introduction
1:29 - The 2 Types of Variation
2:42 - How to distinguish between common and special cause variation (The Key Elements of a Control Chart)
3:44 -RATIONAL SUBGROUPING explained
5:29 - EQUATIONS for the control limits create an X-Bar and R Chart
6:53 - CONSTANTS needed to calculate the control limits for the X-Bar and R Chart
8:28 - EXAMPLE of an X-bar and R Chart
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[@_M_D_M_]

Shut down all other videos on KZbin for Xbar-R Charts. This is enough. Gold Standard. May the force be with you.

[@CQEAcademy]

THANKS!!!!

[@ImanFahmi]

Actually, and without exaggeration, you are the best tutor I have ever seen explaining TQM & Six Sigma, May Allah bless you. A bunch of thanks, Sir.

[@CQEAcademy]

Wow, thank you so much Iman!!! I am extremely blessed, and I want to be a blessing to others!

[@ZenbeworkGirma]

this is amazing that I was struggling for 2 weeks on this topic and you video simplify it. love it

[@annastayinathome4495]

Hello Sir! I missed a lecture in my undergraduate studies and you saved my exam score! Your method of explanation is so simple and yet comprehensive. I cannot thank you enough. Your work has helped many people, may you be blessed.

[@fayadali6722]

Hello Sir. I just wanted to thank you so much for taking the time to produce these KZbin videos. Your method and style of teaching helped me pass my ASQ-CQA exam yesterday. Thank you, Thank you!

[@ashb3390]

Thank you! I’m currently studying six sigma and this has helped me understand the components of the xbar and r chart. Showing a step by step explanations with visuals has helped me so much!

[@CQEAcademy]

Hey Ash, I'm glad the video was helpful!!!!

[@TheEngineeringToolboxChannel]

Great video! Love seeing someone who really understands this teaching it. Too many people on youtube are just slapping +/- 3x the global standard deviation on their line charts and calling it a control chart.

[@jerrychen8715]

Does that +/-3x global stv still senstive enough to capture the abnormal signal? what is the pro and cons for those 2 methods?

[@TheEngineeringToolboxChannel]

Global standard deviation is far less sensitive to special causes because it includes ALL variations ALL AT ONCE with no regard to time in its calculation. This includes special cause variations which tends to heavily skew your limits. The entire purpose of a control chart and its calculations is to identify significant differences between short term (within subgroup) and long term (between subgroup) variation. For a stable process you would expect the short term outputs of a process to be the about same as the long term outputs.

[@rodolfoallpas5527]

Man, this is amazing information, I just got a bunch of information that was explained to me in a 3 weeks course, and you explained it so smooth!!! Thanks for your content, sir!!

[@CQEAcademy]

You're absolutely welcome Rodolfo, and thanks so much for the great feedback and positive comment!

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Really Loved Your Explanation : )👌👌👌

[@CQEAcademy]

Thanks so much Devanshu!!

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Thank you so much! There's a reason why you have no dislikes on this video, because you're awesome!!!

[@CQEAcademy]

wow, thanks so much!!!! I appreciate the awesome feedback!

[@kelvinWambua-tn3kc]

Helpful. In kenya, we say, "Asante kwa kazi nzuri."

[@anniem824]

I have struggled with this concept for a while, and now get the basics to move forward again. Thank you!

[@CQEAcademy]

Glad it was helpful!

[@colouroflife5504]

Simplest explanation. Thankyou. You save me.

[@thishaniholdenberg9086]

you explain right to the point, the exact points we need, Its a huge help for students who come across these modules among other science subjects and has no basic knowledge, Thank you !👏

[@CQEAcademy]

You're absolutely welcome!!!!

[@mercerconsulting9728]

I teach LSS certification classes, and this video is worth sharing with my students becuase it is so clear, consise, and easy to follow.

[@greenbeltacademy]

Thanks so much!

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Thank you so much for this much needed video, gained a much better understanding 👍🏾 appreciate your help

[@plalelal]

Great video presentation and explaination!

[@yvettesalgado1081]

So much helpful then my textbook for my upcoming exam! Thank you for taking your time ! 🙏🏻

[@CQEAcademy]

Thank Yvette!!! You're absolutely welcome, I'm just glad I was able to help you!

[@Absurd-Indian-Guy]

I have a quiz today and I randomly came across your video. This helped me grasp the concept entirely. Thank you so much. Subscribing!

[@odalfrypolonia3099]

amazing video it was easy to follow. thank you.

[@jacqueshollands5630]

Best video on this topic on KZbin

[@CQEAcademy]

Wow, thanks Jacques!!!

[@danielhabteyes8327]

Great tutorial! Thank you Andy.

[@CQEAcademy]

Thanks! I'm glad you liked it!

[@lizzy6805]

Very helpful video. Thank you CQE Academy.

[@CQEAcademy]

You're welcome Lizzy!!!!

[@suthashenyperumal5352]

I managed to learn about X bar R chart fast and clearly. Thanks for the great teaching!

[@greenbeltacademy]

You're absolutely welcome!!!!

[@minimonie9825]

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This is exactly what I needed

[@gillianreyes2974]

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Thank you so much! This video saved my day.

[@CQEAcademy]

Wow thanks Naveena, I'm glad you enjoyed it!! And thanks for the comment!

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This is a lifesaver, my friend!!!!! Fantastic! Thank you so much.

[@CQEAcademy]

You're welcome Tammy!!!

[@alanthomson477]

Great vid. Has really helped me to understand the process. Thanks

[@CQEAcademy]

You're welcome Alan!

[@hfulong]

This is so easy to follow. Very helpful. Great work!

[@CQEAcademy]

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Thank you for clearly explaining the critical acceptance of defect rate per type of product.

[@CQEAcademy]

You're welcome!!!

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[@CQEAcademy]

You're welcome!!

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[@CQEAcademy]

Thank you!

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Your VDO is very crystal clear short but sharp! Thanks from Thailand

[@CQEAcademy]

You're welcome!!!!

[@haroldchrist5174]

thank you so much. this is really easy to follow.

[@CQEAcademy]

You're welcome!!! I'm glad you enjoyed it and found it easy to follow!

[@reynardvandergrijp2681]

Best explanation I have found, thanks a lot

[@greenbeltacademy]

Wow, thanks Reynard!!!

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[@CQEAcademy]

You're welcome!!!

[@ravindrajoshi78]

Excellent!!..

[@theronaldo84]

Well explained, thank you

[@CQEAcademy]

Glad you enjoyed it! -Andy

[@bakihanma1680]

extremely helpful !

[@amsyarfahmi4565]

Good explanation. Thank you andy.

[@CQEAcademy]

You're welcome Amsyar!

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Thank you so much for the great explanation! Really saved me the trouble of understanding my prof's terrible slides xD

[@CQEAcademy]

hahahaha, you're welcome!!!

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Thank you so much for this video !!

[@CQEAcademy]

You're welcome!!!!!!!

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Very helpfull, easy to follow!

[@CQEAcademy]

You're welcome!!!

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Thank you so much for sharing your knowledge Sir! I received my B.S. in Chemical Engineering in Mexico a few years back. I am a naturalized American citizen now. What are the requisites to apply for the CQE exam? I'd really like to enroll in your academy. I enjoy your videos a lot but more importantly the way you teach is very easy to understand.

[@CQEAcademy]

Hey There!! I'm glad you enjoyed that video! Okay about the requirements to sit for the exam, check out this video: kzbin.info/www/bejne/p4GveKiOjrWLi6s And then to join the academy, check out this free course: cqeacademy.teachable.com/p/top-10-topics That free course will also come with details about the full course - The CQE Master Class

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Thank you I really needed this for my work .This was very helpful

[@greenbeltacademy]

You're welcome!

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This is amazing 🤩

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[@CQEAcademy]

You're welcome!

[@pop-saiyan1193]

You a star, thank u...I loved the simplicity, thanks man

[@CQEAcademy]

Thanks!

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[@CQEAcademy]

You're welcome!

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[@CQEAcademy]

You're welcome!

[@dsavkay]

Amazing content thanks!

[@CQEAcademy]

Thank you!

[@ohheydarciemae1121]

I studied this in college and didn't understand it. Man, I wish this video was available to me back then!

[@CQEAcademy]

Thanks Darcie!!!!

[@mubashartariq4521]

Effectively explained

[@greenbeltacademy]

Thanks so much!!!

[@Blackshark553]

very Excellent

[@akanksharai1366]

Well explained with clear presentation I really like your videos, because after seeing that I haven't any doubts 👍

[@CQEAcademy]

Awesome, thanks for the feedback, I'm glad you like them!

[@akanksharai1366]

@@CQEAcademy also make a video on MSA

[@CQEAcademy]

@@akanksharai1366 will do! I'm sure i'll create a video on MSA here in the next 2 months or so. BTW - feel free just to call me Andy :)

[@ravindrajoshi78]

Excellent !! great , Thank you!! do you have all the formulas sheet for calculating control charts values

[@likkileaks7590]

i am from india this helped me very much for my exam tomorrow thank you very much....

[@user-fh7zl6ud4m]

Thanks Again.

[@user-mv6ef5vo4i]

Dear Andy, I need to select a control chart to follow up our customer complaints(for CAPA triggers) , we produce single products (not batches) and there are many attributed customer complaints categories (such as: uncomfortable, broken, wrong parameters ,etc..). number of manufactured products and number of complaints varies each month. My best pick is P chart where I divide the total number of complaints received each month by the number of manufactured products from the previous month (if on January we produced 100 products and on Feb we received 10 complaints then my data point is 10/100=0.1), obviously the only control limit in my interest is the UCL. Do u think I picked the proper control chart? would like to hear your thoughts in general:)

[@rellappanmech1111]

Thank sir. students can easily understand

[@CQEAcademy]

Thanks, I'm glad you enjoyed it!!!

[@sunnyteo7052]

Thank you for sharing and very clear explanination on setting up the UCL & LCL. How frequent do we need to review and recalculate the Control Limit?

[@andyrobertson566]

Hey Sunny! That honestly depends on your process, and how stable and mature it is, and there is no hard and fast rule. If you go-live with a control chart and your process appears to be stable over time, then that re-calculation does not have to happen that often. If you go-live and your process is not stable, you can do both - address those sources of special cause variation, and re-calculate your control limits. But do make sure not to include any OOC (Out Of Control) data points when calculating those control limits.

[@zzxczxcc502]

Thank you .. sir . 💟

[@CQEAcademy]

You're welcome!!!

[@chongkl534]

I have a few questions, I hope that you can help me. 1) How about for subgroup more than 25? 2) Can I calculate the UCL and LCL myself without referring to the constant? especially for big subgroup. 3) I have different orders for a product (mean same setting but different manufacturing date with different batches of raw material), each order with certain number of jumbo rolls, each jumbo rolls will be checked at certain meter length, each meter length will be checked several position from left to right. Should I consider all result is 1 jumbo roll as 1 subgroup and all result in 1 order as 1 subgroup. 4) If we do not use software and only excel, how should we monitor the control chart as we need to calculate the mean, UCL and LCL very frequent?

[@CQEAcademy]

Hey Chong! For question #1, most tables stop at 25. . I tried to google it but couldn't find anything larger. Honestly, after 25 samples, you should stop using the range value and start using the standard deviation (X-bar and S chart). That transition to the S chart usually happens around 10 samples. For #2, no, you need to constants to calculate the UCL and LCL. You might not need the table I guess if you have the constants memorized. For #3, the question here is all about rational subgrouping, and you want to minimize the variation within a sub-group. I doubt you could argue that all of the measurements on a single roll are 1 rational subgroup. It seems more rationale that whenever you take multiple samples at each meter in length, those measurements would be considered a single rational subgroup. Honestly without knowing your process better it's hard to say what a rational subgroup is. #4, there are excel spreadsheets to perform all of the control chart calculations (UCL, LCL, etc), all you have to do is type in the measurement data

[@samuelorozco5984]

Great explanation! I think it would be great if you could include some analysis for what the case would be if we include intermediate lines (+/-1 stds & +/-2 stds). Also, what would the conclusion be if we plot a R point outside the UCL, but the x bar plot is within the UCL and LCL. My understanding would be if the R is out of control, the X bar is inaccurate. But does that necessarily mean that x bar is out of control as well, or is it simply x bar in control and R is out of control? Thanks

[@CQEAcademy]

Hey Samuel!!! Great suggestion, that's definitely a good future video! okay, so it is possible for special cause variation to impact your R chart, but not your X-bar chart. That's why we have both charts, because it's important to monitor both the center of your process (X-bar) and the variation within your process. And either chart can alert you to special cause variation!

[@sierrafreeman2793]

God bless ur soul now i wont fail my exams thank u so much

[@CQEAcademy]

hahahaha thanks!!!! I'm glad you love it!! -Andy

[@narimansarafan1242]

perfect man

[@SameeraPriyadarshana76]

Well explanation ....!!!!!!!!

[@CQEAcademy]

Thanks Sameera!!

[@thiagobianchini9972]

Is there a table with more than 100 sample size for A2 and D4? Or how can I calculate those?

[@ThePrajendr]

Thanks for the video! What do you recommend when we have much larger subgroup sizes? And do you have any recommendations for how to create the centerline? I imagine it's a rolling statistic rather than something static?

[@coolshian]

Same questions too 🙋

[@editingandffqueen7907]

Your the best teacher ❤❤❤

[@CQEAcademy]

Thanks so much!

[@westclark9439]

Super helpful!!! One Question: can the Y values for the Xbar and R chart chart be negative?

[@CQEAcademy]

Hey West, Generally the answer is no, unless you're measuring some attribute that can also be zero. For example if you were monitoring the temperature of a cold process, you could realistically measure temperature values below zero. However, if you're simply measuring a small attribute that can never be a negative number, and your lower control limit is a negative number, the general practice is to move that up to zero. -Andy

[@gr1msasor14]

wow thanks man

[@rushikeshsanap1014]

Love you sir from India

[@CQEAcademy]

Thanks Rushikesh!!!!!!!!

[@19manu06]

You are a genius. Make more videos, Awesome!!!!!!!!!!

[@CQEAcademy]

Thanks! I'm glad you like it!

[@rupeshchoudhari96]

🔥lit explanation I was going through hard time of understanding this... Now I thought how easy it is...

[@CQEAcademy]

Awesome, thank you Rupesh!!! I'm glad I can help you grow!

[@rupeshchoudhari96]

@@CQEAcademy Ya, it helped me in my diploma exam... 😅 Last minute studies!

[@CQEAcademy]

@@rupeshchoudhari96 fantastic, what are you getting your degree in?

[@rupeshchoudhari96]

@@CQEAcademy I'm currently in last year Diploma (Mechanical)

[@CQEAcademy]

@@rupeshchoudhari96 Best of luck!!!! I got my degree in mechanical. Let me know if there are any other topics that you'd like to see. -Andy

[@greteldsouza3979]

thank you

[@CQEAcademy]

You're welcome Gretel, and thanks for the comment!

[@kaneki4403]

thanks for clearing it up. also i'm your 1000th like 👍

[@andyrobertson566]

Awesome, thanks Kaneki!!

[@manikandansrinivasan9816]

Sir, how did you find the A2 value? What is the formula behind it?

[@CQEAcademy]

Hey Manikandan!! I love this question - they actually can be derived from the d2 values, and sample sizes.

[@surnamegm]

Hello! Great explanataion! One question: at the rational subrouping section, how to imagine the 5 measurements / groups? Does it mean: 5 sample parts are selected from the production same time, and 1-1 measurement is carried out on them or 1 product is selected and that is measured 5 times, so this 5 measurements give the "subgroup"? Thank you

[@CQEAcademy]

Hey Great question!!! Okay, so a rational subgroup of 5 would mean 5 unique samples measured 1 time. It's not a single sample measured 5 times. That type of variation would reflect the variation in the measurement system, not the variation in the process. -Andy

[@surnamegm]

@@CQEAcademy Oh, thank you for the quick reply! I wondering, how this kind of UCL and LCL calculation can happen in the reality. Imagine there is a production line, (a work station e.g. turner machine). How can I set up the control line for the process? Should the control lines be there, before he begins the job? As planned, every half hour a sampling will be measured (e.g 3pcs/sampling). After 4 hours there will be 8 subgroup- measurement results. After I have 8 result, i calculate the control line. 1. How the process will be monitored before the control lines' calculation, in the first sevaral hours? 2. What is the meaning of the control lines' calculation, if the next and next and next subgroups' result will again and again change the UCL and LCL values? Sorry for the detailed question, i just would like to understand this very well.

[@CQEAcademy]

@@surnamegm Hey There, Okay, so generally, you want to collect around 25 sub-groups to calculate the control limits. Until you have control limits in place, just consider the chart to be a "run-chart" with no control limits. Also, before calculating the control limits using those first 25 sub-groups, you want to feel reasonably certain that the process was only experiencing normal (inherent) variation. You should not re-calculate the control limits for each new data point. However it's not unreasonable to re-calculate the control limits if a change is made to the process. This is something that you'll get better as assessing over time (the need to re-calculate the control limits). It's hard to create rules for this scenario because every process is different. Hopefully that helps! -Andy

[@surnamegm]

@@CQEAcademy Thank you very much!

[@CQEAcademy]

@@surnamegm You're welcome!

[@samaticsgoodluck4793]

Pretty cool

[@CQEAcademy]

Thanks!

[@Name-ur6oj]

Hi! May I ask, where did you make your x-bar and r chart? Is there any particular application or website you recommend for me to use in making a control chart? Thank you!

[@CQEAcademy]

Hey There!! I made that control chart in Excel

[@Name-ur6oj]

@@CQEAcademy Oh I see, thank you!

[@CQEAcademy]

@@Name-ur6oj You're welcome

[@snoringdragon1980]

Hi, what is the "underlying distribution" of a process?

[@vijaybenz9741]

studying this topic for my engineering exams

[@Muhammadharis-ds3tr]

May Allah bless u thanks alot

[@CQEAcademy]

You're welcome Muhammad!!!

[@sachinbr7262]

is the time period between each sub groups a standard. For example if the time period between each sub groups are 24 hours then what is the use of using control charts because if the time period is too long we cannot estimate fast how our process is under control. Please answer sir

[@agradhanurwedhasakti4865]

Thanks for your videos, it really helps a lot. A quick question though, what if I measure each sample 2 times? Do I need to count each of them as 2 samples or as 1 sample but using their average measurement?

[@CQEAcademy]

Hey Agra, I assume that when you take those 2 measurements, that you're measuring the same characteristic - not two different things (dimensions, etc). I haven't run into that situation before - why would you measure the same sample twice?

[@agradhanurwedhasakti4865]

@@CQEAcademy Yes, it is the same characteristics but 2 replications. I am not really sure why there are 2 replications because I just retrieved it from old data, probably because there is a doubt in the gage precision

[@CQEAcademy]

@@agradhanurwedhasakti4865 That's what came to mind when I first read the two replicate measurements, that someone was worried about gage precision. Honestly, what I'd do is run a Gauge R&R, and if the R&R is acceptable - go down to only a single measurement! That might be a huge form of waste (over-processes) by measuring the same sample twice. And if the gauge R&R is bad. . . it might be time to find a new gauge - too much precision should not be overcome by repeated measurements.

[@jarodjenkins]

Great information. This is the youtube channel i've been looking for! fucking amazing

[@CQEAcademy]

Wow thanks so much Jarod!!!!

[@adrianaescuder5290]

hi! One question, if we calculate the icl and lcl by hand, how can we get the z (number of normal standard deviations)? Thanks :)

[@andyrobertson566]

Hey Adriana! In your example, do your UCL and LCL change over time, or are they fixed after you perform the calculation?

[@brudo5056]

OK, this is about starting the charts but is there also a video or explanation what and how to act when the process gets out of control... when and how to recalculate limits, eliminate outliers etc... Thanks for this intro anyway. Greetings.

[@ptrice1213]

Is the moving range chart and x-bar chart the same?

[@akakarun8]

Finally today I got to know about Rational Subgroup. Thanks from India.👍

[@CQEAcademy]

Awesome, glad I could help!!!!

[@vikasasodariya1368]

Great

[@CQEAcademy]

Thanks Vikas!!

[@mishras.k.2896]

In the last slide for X Bar chart I think the lower line 3.9 value should be rename as LCL not UCL. But very fine analysis.

[@CQEAcademy]

Great catch, and you're correct, thank you though!!

[@cashmetanzania6826]

Do we need the same number of sample size for all sub groups?

[@CQEAcademy]

Great question! I would recommend using a consistent sample size over time because it will make it easier to manage the control chart over time. Changing sample sizes is not impossible, but you have to make sure that as you change the sample size you don't violate the requirement of having a rational subgroup, and you will have to re-calculate your control limits with your different sample sizes.

[@semester5825]

teaching level 😊

[@CQEAcademy]

Thanks!!!!!!

[@cocopop111]

Question: at which point do you conclude that a process is out of control ?..... how many data points out of 2 or 3 sigma. Is there a standard that shows which qualifies of a process not in Control and needs action?

[@CQEAcademy]

Great Question!!!! Okay, so I hinted at this in the video, but there are other ways (besides being outside the 3-sigma control limits) where the data indicates that the process might be out of control. There are other rules - the most popular being the Western Electric Rules (en.wikipedia.org/wiki/Western_Electric_rules) that you can use to also detect patterns in your data that indicate that your process is out of control. Also, I should say, that it is completely possible that your process have a single data point outside of the control limit, and the process is still only experiencing normal process variation (there's a 0.3% chance that this could happen). So when you get a point that's "out of control", you should start the investigation to determine that special cause of the variation.

[@cocopop111]

Ok great thanks ....

[@CQEAcademy]

@@cocopop111 You're welcome!

[@amirjavadkar1632]

Excellent❤❤❤, One question What if we have different tolerance for each subgroup, For example for subgroup 1 we have +/-2 and for subgroup 2, +/-3 and so on, Have we calculate process capability in this condition?❤❤❤❤❤❤