QA- lec 5

Question 1

Control charts

Answer 1

• Shewhart plots
• Cusum plots
  
  • Cumulative sum chart

Question 2

Random and systematic error

Dot plot

Answer 2

Question 3

Standard deviation of the entire population

Answer 3

Question 4

Standard deviation of the population based on a sample

Answer 4

Question 5

Real mean

Answer 5

• Tank of product has real mean (u) and an actual SD (sigma)
• Samples from tank have a mean and SD which is an estimate of the true mean
• In order to use the sample results to estimate the tank (population) deviation (s) use n-1

Question 6

Properties of the normal distribution

Answer 6

Question 7

Confidence intervals

Answer 7

• n= sample size- replicate in sample
• Confidence limits rounded to
• 95% CI= u= x + 2s / Square root of n
• (x= true mean) 2s= pop Sd n=replicatres in sample
• 99.7= same but with 3s

Question 8

Shewhart charts

Answer 8

• Over a long period of time we can assess the population deviation (sigma) (process capacity)
• n= sample size
• u= target mean
• CI rounded to
  
  • warning lines
  • Action lines

Question 9

Shewhart chart for mean values

Answer 9

Question 10

Areas under the normal curve

Answer 10

• 1 in 45 obeservations normally fall above (below) 2sigma
• 1 in 750 normally fall above and below 3sigma

Question 11

Control charts Shewhart plots

Answer 11

Question 12

Controls using shewhart plots

Answer 12

• Out of control examples
  
  • Two successive points outside warning line
  • One point outside action line
  • Eight successive points lying one side of the target value line
• Establish other warning levels to enable correction before production stops
  
  • E.G. six successive points lying one side of the target value line

Question 13

Cusum plot

Answer 13

• ARL- average run length
• This is the average number of measurements required to deyect a change in the process has changed
• This period of time can be length in shewhart plots
• This can be reduced by using cusum charts

Question 14

Shewhart v cusum plot of data

Answer 14

Question 15

Use of V-mask Initial data

Answer 15

• If points fall above or below the mask then the results are said to be out of control

Question 16

Data integrity

Answer 16

• Current regulatory hot topic
• The extent to which all data are complete, consistent and accurate throughoutout the data lifecycle
  
  • From initial data collection and recording, through processing (including)