Transcript • A designed experiment is a study in which there

• A designed experiment is a study in which there
is an intervention by the experimenter to impose
treatments on the experimental units - look over
Example 2.1… treatments are combinations of
levels of the factors. The response is measured
for each unit and comparisons are made between
the treatments … often the treatment groups are
compared with a control treatment (or a control).
• Three important principles of experimental design
are:
– randomization
– control
– replication
• The experimental unit might be different from the
measurement unit, the physical entity on which
the response is measured… see Ex. 2.2
• The experimental error is “the variation in the
response among expermental units assigned the
same treatment and observed under the same
conditions
• Review the first example in section 2.5:
– p.26: “… evaluate the wear characteristics of 4 major
brands of tires.” factor(s)=?; levels=?; treatment(s)=?;
response=?
– what are the “controlled variables” or “extraneous
factors” that are the same for all brands of tire?
– there are many possible designs
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randomly assign a brand of tire to a car…
randomly assign 4 tires to a car…but see Tab.2.1
block by car and randomize the brands Tab. 2.2
block by car and position on the car and randomized
the brands Tab. 2.3 (Latin Square)
• Look at example #2 (p.29) “…examine the effects
of temperature and humidity on the bonding
strength of the new adhesive”
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factors?
levels?
blocks?
treatments?
response?
replications?
experimental and measurement units?
• Look at the one-at-a-time approach to factorial
designs vs. the full factorial treatment structure
• HW: Work through exercises 2.6-2.9 for next
time. Make sure you understand the terminology
in this chapter…