Lecture 4 Measure phase
Measure phase
- Objectives
- Data collection
- Variation
- Six Sigma & process capability
Objectives to measure and understand the performance of the current process
- Input delivery and quality demands for suppliers
- Process internal process measurements
o Inclusive: quality and delivery demands for the internal customer
o Loss and throughput regarding output demands
- Output measurements to assure that customer demands are met
Preparation for analysis start with abstractions
- Y = f(x1, x2, …, xn)
- Y relates to the outputs
- X relates to the inputs
- Identify the X’s that might explain variation in the output measures
- Collecting data efficiently both the Y’s and the suspected X’s
Data collection
Develop a data collection plan
- Clarify collection goals link customer requirements to output measures
- Develop operational definitions and procedures operational definitions, new data, types
of data, collection and recording of data & sampling
- Plan for data consistency and stability validating instruments
- Begin data collection historical data, new data, experiments make into graphs and stats
- Continue improving measurement consistency
Variation
- All repetitive activities within a process show variation
- Input, process and output results show differences = variation
- Variation is the voice of the process
- All variation is caused by something
- There are 2 major groups of causes how might help to select appropriate managerial actions
o Common causes the result will be a stable system
o Special causes the result is an unstable system or unpredictable
Variation in processes statistics is essential
- Standard normal distribution
o µ = 0 and σ = 1
o Standardise: change into Z-values
, Density function
Computational equations
Z-value used for the variable which follows a standard normal distribution
- A negative Z-value indicates that the X value is smaller than the average
- A positive Z-value indicates that the X value is bigger than the average
- Z = ( X - µ ) / σ (X – average) / standard deviation
P-value the chance that…
- Two fundamental laws
1. P (z > Z) = P ( z < Z) within a normal distribution graph, this will be on the left side of
the line that will be drawn
2. P (z > Z) = 1 - P ( z < Z) within a normal distribution graph, this will be on the right side
of the line that will be drawn
Continuous data
- Any value > 0 is possible
- No gaps between possible values
- Time, money, length, weight
- Sample size = 30
Discrete data
- only certain values are possible
- Gaps between possible values
- Number of damagers/parts, number of sales in a week, good or bad, success or failure
- Sample size = 50
Sampling collection of only a portion of the data that is available or could be available
- Using the data in the sample to draw conclusions
- Often impractical or too costly to collect all the data
- Sometimes data collection is a destructive process (taste testing, collision tests)
- Sound conclusions can often be made from a relatively small amount of data
Confidence interval (the normal distribution)
- µ = the real average of the population
- σ = the real standard deviation
- ẍ = the average
- S = the standard deviation from the sample
- Ex. A 95% confidence interval stipulates the range of a interval where you will find the
population average with a 95% certainty
- More measurements in the sample, gives a more narrow margin of the confidence interval
more certain pronouncement
- Reliability does not implicate the accuracy of the measurements
Voordelen van het kopen van samenvattingen bij Stuvia op een rij:
Verzekerd van kwaliteit door reviews
Stuvia-klanten hebben meer dan 700.000 samenvattingen beoordeeld. Zo weet je zeker dat je de beste documenten koopt!
Snel en makkelijk kopen
Je betaalt supersnel en eenmalig met iDeal, creditcard of Stuvia-tegoed voor de samenvatting. Zonder lidmaatschap.
Focus op de essentie
Samenvattingen worden geschreven voor en door anderen. Daarom zijn de samenvattingen altijd betrouwbaar en actueel. Zo kom je snel tot de kern!
Veelgestelde vragen
Wat krijg ik als ik dit document koop?
Je krijgt een PDF, die direct beschikbaar is na je aankoop. Het gekochte document is altijd, overal en oneindig toegankelijk via je profiel.
Tevredenheidsgarantie: hoe werkt dat?
Onze tevredenheidsgarantie zorgt ervoor dat je altijd een studiedocument vindt dat goed bij je past. Je vult een formulier in en onze klantenservice regelt de rest.
Van wie koop ik deze samenvatting?
Stuvia is een marktplaats, je koop dit document dus niet van ons, maar van verkoper SpeedyGonzales. Stuvia faciliteert de betaling aan de verkoper.
Zit ik meteen vast aan een abonnement?
Nee, je koopt alleen deze samenvatting voor €3,99. Je zit daarna nergens aan vast.