5
STAT 101 Worksheet: Experimental Design
Identify the components of the following experiments.
Example: A researcher studies engine wear using 3 oil weights (5W30, 10W30, and 10W40) and three oil additives (teflon, SlikStuff,
and Slip 80). Thirty-six engines are available for the study. Each engine is run with one of the weights and one of the additives, and
after 1000 hours of running, the reduction in thickness of the piston rings is measured.
Units: 36 engines
Response Variable: piston ring thickness
Factor(s) & Levels: Two: 1) Oil weight, with three levels ; 5W30, 10W30, 10W40
2) Oil additive,with three levels: teflon, SilkStuff, Slip 80
Number of Treatments: Levels of factors multiplied = 3 * 3 = 9
Diagram:
36 engines
randomly
distributed to nine
treatments.
Oil weight (down); Oil viscosity =>
5W30
10W30
10W40
Teflon
5W30 & Teflon
10W30 & Teflon
10W40 & Teflon
# of units per treatment: 4 (36 engines/9 treatments)
SilkStuff
5W30 & SilkStuff
10W30 & SilkStuff
10W40 & SilkStuff
Slip 80
5W30 & Slip 80
10W30 & Slip 80
10W40 & Slip 80
Collect results,
analyze, report
conclusions
Experiment #1 – Lazy Susans: A manufacturer of lazy susans performs an experiment to study reduction of friction using two types
of ball bearing, one type with teflon coating and another of plain steel with tiny pores to hold oil. Also, three different viscosities of
oil (thin, medium, and thick) are used in conjunction with the ball bearings. Thirty lazy susans are available for the experiment. Each
lazy susan is spun to the same speed, and the time required for them to stop by themselves is recorded.
Units:
Response Variable:
Factor(s) & Levels:
Number of Treatments:
# of units per treatment:
Diagram:
Experiment #2 - Electricity Use Monitors: Many utility companies have introduced programs to encourage energy conservation
among their customers. An electric company considers placing electronic indicators in households to show what the cost would be if
the electricity use at that moment continued for a month. Will the indicators reduce electricity use? Would cheaper monitoring
methods work almost as well? One cheaper approach is to give customers a chart, and information about monitoring their electricity
use. An experiment is designed to compare these two approaches, as well as using no method of monitoring. 60 single family
residences in the same city are willing to participate. The company assigns 20 residences at random to each of the monitoring
methods. One group of 20 will use no method of monitoring. The electric company is interested in the total electricity used by the 60
residences over the course of one year.
Is this an experiment? Why or why not?
What are the units?
What is/are the dependent (response) variable(s)?
What is/are the factor(s)?
How many levels of each factor are there?
What is/are the treatment(s)?
Diagram:
Experiment #3 - Package Liners: A manufacturer of food products uses package liners that are sealed at the top by applying heated
jaws after the package is filled. The customer peels the sealed pieces apart to open the package. What effect does the temperature of
the jaws have on the force needed to peel the liner? To answer this question, engineers obtain 20 pairs of pieces of package liner.
They seal 5 pairs of each at 250 degrees F, 275 degrees F, 300 degrees F, and 325 degrees F. Then they measure the force needed to
peel each seal.
Units:
Response Variable:
Factor(s) & Levels:
Number of Treatments:
# of units per treatment:
Diagram:
Experiment #4 - Instant Breakfast: A food company assesses the nutritional quality of a new “instant breakfast” product by feeding
it to newly weaned white male rats. The company is interested in a rat’s weight gain over a 28-day period. 30 rats are divided into
two equal groups for the experiment. One group will eat the new “instant breakfast,” and the other group will eat a standard diet, but
otherwise receive exactly the same treatment as the 15 rats being fed the “instant breakfast.”
Units:
Response Variable:
Factor(s) & Levels:
Number of Treatments:
# of units per treatment:
Diagram:
Experiment #5 - Corn Varieties: New varieties of corn with altered amino acid content may have higher nutritional value than
standard corn, which is low in the amino acid lysine. An experiment compares two new varieties, called Opaque-2 and Floury-2, with
normal corn. The researchers mix corn-soybean meal diets using each type of corn at each of three protein levels, 12% protein, 16%
protein, and 20% protein. They feed each diet to 10 one-day-old male chicks and record their weight gains after 21 days. The weight
gain of the chicks is a measure of the nutritional value of their diet.
What are the experimental units?
What is/are the dependent (response) variable(s)?
What is/are the factor(s)?
How many levels of each factor are there?
What is/are the treatment(s)?
How many experimental units will be required in this experiment?
Diagram:
f: Worksheet – Exp design