DESIGN OF EXPERIMENTS

							DESIGN OF
EXPERIMENTS
           DOE

  STATISTICAL EXPERIMENTS
      By Mike Newtown
• Why experiment?
  • To increase knowledge about a process
• What good is increased knowledge?
  • Increase the output of the process
  • Reduce variability
  • Produce a robust product that is not
    influenced by environmental factors
• Why Experimental Design?
 • To obtain valid conclusions from
   an experiment
 • To yield the maximum amount of
   useful information with the least
   amount of experimentation
   (experiments cost money)
• Types of scientific studies
  • Experimental- variables of interest
    can be controlled
  • Observational- variables can not
    be controlled (data analysis)
• Choose at least two factors that
  influence the output of the
  experiment
• Rank order the factors
• Determine levels of control
• Consider the resource available
  to perform the test
Good Experiments
Should:
• Eliminate know source of bias
• Guard against unknown source
  of bias
Variation

• Experimental Errors:
  • Setting not exact enough to be
    fixed exact same point each time
• Measurement Errors:
  • Inability to obtain exactly the
    same measurement on the
    successive, identical test runs
Combat Variation

• Standardize procedure
• Collect larger number of data
  points

Accuracy & Precision vs. Cost
Scientific Method

•   Investigate situation
•   Define problem clearly
•   Formulate hypotheses
•   Select appropriate experiment
•   Conduct experiment
•   Analyze results
•   Draw Conclusions
•   Take action on conclusions
Statistics

•   Mean
•   Range
•   Standard Deviation
•   Z tables

    Are very important in analyzing
    data
Hypothesis Testing

• In an experiment, we don’t test
  to see if our ideals are right, we
  test to see if they are wrong.
• Null Hypothesis (Ho) statement
  of ideal as if nothing unusual
  was occurring
• Alternative hypothesis (Ha)
Lets see how this works

Problem: Sub dough at Subway
Factor A: dough type (type 1 & 2)
Factor B: oven temperature
            (125 and 140 Celsius)
Factor C: bake time (8 mins or 10
                    mins)

  See board work
Your Turn to try

• Paper Helicopters
• See ENGS 101 Blackboard Site
• Team competition for the
  longest flight time.
• Using your experimental data
  taken Thursday in class design
  the optimal helicopter.
• This is 3 factor 2 levels
  experiment