Hi everyone how are you today I bring one more new topic for you named as What is I-MR chart? Its use and importance.
As you know I MR chart is stands for individual moving range which play very important role to check the process variation easily.
It is the easiest type of chart to detect the process valuation.
It is less time consuming charts to know the variation of the process and understanding It carefully.
So let us back to topic What is I-MR chart? Its use and importance without wasting time.
What is an I-MR Chart?
The acronym I-MR stands for Individual Moving Range , As the name describe it self that it is plot of individual and moving range for collected sample over a period.
It is also named as Shewart Charts because it was introduced by Walter Shewart.
It helps to check the process variation over a time and give alarm about variation if it goes out of control. The alarm helps to identify the cause behind the variation either it is common or special.
Uses of I-MR chart:
It is used to check process variability for sample collected.
It is used when data is continuous
It can use on small sample size which makes it less time consuming
Check the cause’s nature in process (common /special cause)
It is used save the cost for collection of large sample which are not feasible
Generally it is used in destructive testing
It gives a picture about how process is performing
Difference between I-MR and X bar R chart
It plot individual data
Check the variation in process which is based on change in range
It plot the data sample to sample
X bar chart
It plot the mean of samples
It used to draw subgroup data
Relation between I-MR chart and X bar R chart:
Above mentioned are the difference between both but as they are statistical tool they can use in series, means X bar R chart can be used in place of I-MR chart where sample size is more and focus is on the mean of data.
When would you use one over the other?
X̅ – R chart to be used when the large data is readily available, where as I-MR chart to be used in case of limited data. I-MR chart to be used when subgroup size is one while X̅ – R chart to be consider when subgroup size is between two & ten, and use X̅ -S chart if the subgroup size is eleven or more.
How to use an I-MR Chart effectively:
First of all to use I-MR chart effectively , It is necessary to make process stable which means there is no an special cause is available in the process.
Than we have to use I-MR chart and monitor the process variation. I-MR chart will give the signal If an special cause is enred in the process or the process is running on common causes.
What are check points for I-MR chart?
Only capture the data in sequence
Only use individual data set in place of sub group averages.
Use only when the process is stable