Question

Match the term on the left with the clues on the right Central limit A. Used to track the mean B. Dividing line between random deviations and nonrandom variations C. Used to track the variance X-bar chart Range-Chart Control limit P-chart D. Normal distribution E. Used to monitor the proportion defective

Answer 1

ANSWER

1. central limit- normal distribution
2. x-bar chart- used to track mean
3. range chart -used to track variance(in range)
4. control limit-dividing line between random deviations and non-random deviations
5. p chart - sue to monitor proportion defectives

EXPLANATION

Central limit

The central limit theorem states that if take random samples from the population , then the distribution of the means of the samples will be approximately normally distributed.

Control chart

The control chart helps us to see how a process changes over time. A control chart has

• central line for the average

• upper control limit and

• lower control limit

The points going beyond control limits are not under control

There are different control charts. Based on data, they can be allotted in 2 categories

1.Continuous data/ Variable data

Variable data takes on a measurable, numeric value (can be infractions e.g. 7.65) . E.g. . height of students in a class

Charts used-

• x- Chart,

• R –chart,

• Individuals & moving R( I-MR)

Suppose in a process, we collect a sample of observation at a time. We have   five observations in a sample. The average of observations gives sample mean

Similarly we collect several samples at different times

We want to know

• Whether the average of different samples are nearly same (under control) . we use X bar chart. xbar chart is used for controlling the variations in the average quality

• Whether the observations in each sample vary widely. We want to make sure that observations in sample do not have a wide range and are closer together . we use range chart .R bar chart is used for controlling the variation in the dispersion of the quality    

2. Discrete Data/ Attribute data

• Attribute data consists of categories.. e.g. Defects or no defects, Yes or No.

• No fractions- we don’t use 1.5 defect . It is either a defect or no defect

• Charts used – P chart, c-chart, u-chart

p-chart is used to control the proportion of defective items in a sample