Maths And Stats Flashcards
How are control charts used to assess quality?
Control charts are used to monitor a process over time by plotting data points and comparing them to control limits
What is useful about control charts?
They help to visually represent a process, are easy to construct and interpret, and track trends while observing fluctuations between statistically derived limits
How to control charts help to identify deviations?
They can identify ‘special cause’ variation to highlight problems and provide early warning signals before rejects are produced
What is considered the enemy of quality?
Uncontrolled variation is considered the enemy of quality, and SPC manages this variability
What is the key principle to distinguish between in SPC?
A key principle is distinguishing between common cause (random) and special cause variation.
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Common cause variation is inherent in the process and likely to continue.
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Special cause variation occurs occasionally and is less likely to recur
What is Acceptable Quality Level (AQL)
AQL is the maximum acceptable percentage of defective items in a batch that is considered satisfactory.
What do AQL sampling plans specify
The sample size (n) to be drawn from a batch and the acceptable number of defects (c) for a batch to be accepted
What is Dixon’s test, and when is it used?
Dixon’s test is a statistical test used to identify outliers in a small sample. It is used when a single value in a data set is suspected of being an outlier, possibly due to a faulty measuring device or other error.
What does Dixon’s test involve?
The test involves calculating a ratio (r) based on the difference between the suspected value and other values in the sample, and comparing it to a critical value based on the sample size. If the calculated r exceeds the critical value, the suspected value is judged to be an outlier.
What is the purpose of regression Analysis
Regression analysis demonstrates associations between variables e.g drug dosage and blood pressure and establishes theoretical models to predict variable values
Define a confidence interval?
A confidence interval is a range of values that is likely to contain a population parameter within a certain degree of confidence
What is the confidence interval
The confidence interval provides a range of values around our estimate, within which we believe the true population parameter lies
What is the confidence level?
This is the probability that the confidence interval contains the true population value, a 95% confidence level means that if we were to repeat the sampling process many times 95% of the resulting confidence intervals would contain the true population parameter.
What does the width of the confidence interval mean?
The width of the confidence interval reflects the uncertainty in your estimate, a narrower interval indicates less uncertainty
