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1answer
20 views

Use daily production as a check on whether monthly production goal is likely to be met

This is a real small business problem, not a homework problem. A monthly production goal is 60000. We want to be sure that say 95% of months meet this goal. The goal is a minimum, so we want to be ...
2
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1answer
39 views

Quality Control Chart for non-normal distributed data

I am interested in building quality control charts for time series data where every data point has different gradation within the range of 0 to 1. For example first data point X1 may be 0.1, 0.2,..,1 ...
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0answers
31 views

What is “the” correct way of calculating Cp/Cpk values for Statistical Process Control?

There seems to be many different methods of calculating Cp/Cpk values in SPC, and I need help in determining which one to use at any given situation. Currently, we need to show Cp/Cpk values when ...
2
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0answers
37 views

Mean number of samples before out of control in p-chart

I'm stuck with this problem on quality control and p-charts. There is a given process, monitored periodically taking samples of 100 items each and counting the number that are defective. In the last ...
12
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2answers
459 views

Why isn't bayesian statistics more popular for statistical process control?

My understanding of the bayesian vs frequentist debate is that frequentist statistics: is (or claims to be) objective or at least unbiased so different researchers, using different assumptions can ...
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0answers
38 views

How to calculate in-control ARL for control charts?

How to calculate in-control ARL for control charts? For example, to design an EWMA Control Chart, how we could conclude that in-control ARL is approximately 500 for Lambda=0.1 and L=2.7? Thank you!
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0answers
20 views

How can plot the kernel distance based multivariate control charts when data set is given?

Need to know any software or code to plot the K-chart for multivariate data.
2
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2answers
106 views

Meta analysis: How to assess the quality of each of the individual studies in a systematic way?

I have a meta analysis at hand. I have reported on the quality of the included studies in a narrative form. But after I was requested about "quality assessment". I guess it might be something else, a ...
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0answers
77 views

Sampling for quality control

I would like to do some quality control study for a set of manufactured components. For a given set, I can draw several samples. Each drawn sample can be either good or bad. My plan is to create a ...
2
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2answers
65 views

Method to remove bad values in time series (bad values known to take on a particular value)

This sounds easy, but I don't know of a good statistical method for it. I have a time series that has (good) data points that range from ~3.5 to 30. The data are collected by an automated sensor. ...
3
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1answer
1k views

Measuring k-means clustering quality on training and test sets

I'm working on implementing streaming k-means in Mahout. The code is mostly done and we're talking about how to integrate the code. As part of the quality evaluations, I want to know how the ...
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2answers
170 views

Data analysis on multiuser environment

I have following environment that I'd like to analyze. My company is divided in two teams: Insert Team (composed by 150 persons) Quality Check Team (composed by 10 persons) Suppose that all ...
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0answers
35 views

Software quality control references

I'm looking for references on statistical quality control of software. My searches have turned up a lot of writing on how to predict the time that software projects will take, and also software ...
4
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2answers
125 views

Algorithim to determine if point is “too far from the average”

Long story short I have a collection of about 30 scripts that manipulate data sets and place them in a database. These scripts report their running times as well as any errors that occur to a ...
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2answers
579 views

Validating data set using standard deviation

Suppose I have two data sets. The average of one data set is 5.5 secs and the standard deviation is 0.0435. The average of the other data set is 5.2 secs but the standard deviation is 0.5123. I know ...
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2answers
275 views

Where can I find online notes about statistical process control?

Please could you someone help me to find online resources related to the topic of quality control (statistical process control)
4
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2answers
296 views

How to judge if a datapoint deviates substantially from the norm

This is Statistics 101, but I'm not a statistician and so can't seem to find the right technical jargon to google. My company collects data at discrete points through time. Today's datapoint is ...
3
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2answers
2k views

How to calculate margin of error for a binomial quality control experiment where only successes are observed (including FPC)?

Wikipedia's Margin of Error entry says that a random sample of size 400 will give a margin of error, at a 95% confidence level, of 0.98/20 or 0.049 - just under 5% given an infinite ...
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2answers
132 views

Looking for aberrations in time based data

Looking at IO latency data for a storage array. When a drive is about to fail, one indication is an increase in the IO operations 'time to complete'. The array kindly provides this data in this ...
1
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1answer
262 views

How to properly set up hypothesis testing in an operations reporting environment

I am in charge of quality control of n = 400 reports. Most of the quality checks are automated, but some have to be manual. I need to figure out how many reports my team needs to check manually in ...
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2answers
127 views

Find degradation rate on a scatterplot

I work for a commercial printing company, and am collecting data regarding the quality of our printing over time (density and dot gains). Essentially, for every job I have a date, a density, and a ...
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3answers
159 views

How to verify extremely low error rates

I am faced with trying to demonstrate through testing an extremely low error rate for a sensor (no more than 1 error in 1,000,000 attempts). We have limited time to conduct the experiment so we ...
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0answers
70 views

Calculate quality estimates for distribution of real data

Imagine I have measured heights of humans (in cm) and show the data in a histogram: ...
3
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1answer
405 views

Software for learning statistical quality control

I'm taking a course in Statistical Quality Control as an elective in my masters program. We're using Montgomery's Introduction to Statistical Quality Control, 6th Edition. The book uses minitab ...
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0answers
73 views

What are some quick initial tests to check the quality of a new dataset? [duplicate]

Possible Duplicate: Essential data checking tests When you are presented with a dataset, what are some quick things you can look for to get a feel of how 'good' the dataset is. ('Good' in ...
3
votes
1answer
109 views

How to assess prevalence of grossly inaccurate data in recorded body weights in medical records?

I have around 5 million observations of weights of patients over the course of a year. Some patients have one measurement during that year and others have 30-40 (or more). I've noticed a great deal ...
1
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1answer
1k views

What is the mathematical difference between Cpk and Ppk?

I am trying to understand the mathematical difference between Cpk and Ppk used in Statistical Process Control (SPC). I have gone through the web but all I found a confusing and more confusing ...
3
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1answer
137 views

Proofreading lots of documents based on small sample

I have gazillion documents (your tax return) that I need to check for correctness, but I don't the manpower nor the will power to read through all of it. Even if I do, I can not guarantee the quality ...
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2answers
1k views

Quality assurance and quality control (QA/QC) guidelines for a database

Background I am overseeing the input of data from primary literature into a database. The data entry process is error prone, particularly because users must interpret experimental design, extract ...
3
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1answer
159 views

Computing unbiased estimators of $\sigma$ for m samples of size n

Three unbiased estimators of standard deviation have been presented in the literature for m samples of size n. The first one is based on the sample ranges and can be obtained by $\hat \sigma_1 = ...
37
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8answers
633 views

How do I get people to take better care of data?

My workplace has employees from a very wide range of disciplines, so we generate data in lots of different forms. Consequently, each team has developed its own system for storing data. Some use ...