Statistics 101: Section L - Laboratory 7
This lab consists of two group activities. You can work in groups of two, three or four but you must work in
a group. For the first activity, you will design an study to determine the best popcorn brand for the money.
For the second activity, you will design and conduct a study to determine the average weight of one M&M.
For both activities, keep in mind the three principles of good experiments: control of outside variables,
randomization and replication within the experiment.
1. Group Activity 1:
Your group must decide what type of microwave popcorn is the best value for the money. There are
4 competing brands of microwave popcorn. Each brand sells individual packages weighing the same
amount. The price is different for each brand’s packages. The amount of popped popcorn varies as
well, from package to package, within a brand and from brand to brand. Your task is to design a study
that will produce data that will help you make an informed decision as to which brand is the best
value.
(a) First decide on a response. What aspect of the popcorn makes it a good value for the money?
How will you measure your response? Be specific.
(b) What are the “treatments” for this study?
(c) What are the experimental units for this study?
(d) Come up with a list of outside variables that might affect your response. You should be able to
come up with at least five. How will you control these variables in your study?
(e) How will you incorporate replication in your study?
(f) From a statistical point of view more replication is better, e.g. 100 experimental units in each
treatment group. From a practical point of view why might you have less replication, e.g. 10
experimental units in each treatment group?
(g) How will you incorporate randomization in your experiment? Be specific about how you will
randomize. From your description I should be able to perform the randomization.
2. Group Activity 2:
In a previous lab we conducted an observational study by selecting bags of M&Ms, weighing their
contents and counting the number of M&Ms in each bag. From the analysis of those data, we found
that using the usual least squares regression to predict contents weight from number of M&Ms was not
very successful. Part of the problem was that we observed numbers of M&Ms in the 20’s and 30’s and
tried to use this data to extrapolate back to the origin.
Your task in this activity is to design and conduct an experiment to obtain a reasonable estimate of
the average weight of a peanut M&M and the average weight of a Ziplock bag using least squares
regression. You will have a tupperware container of M&Ms, a Zip lock bag, you should put M&Ms in
the bag and weigh both the bag and contents, and a scale to conduct the experiment.
(a) What is the response variable for the experiment?
(b) What is the explanatory variable for the experiment? What levels of this variable will you use for
your “treatment” groups?
(c) What are some outside variables that may affect the response? How will these be controlled in
your experiment?
(d) How will you incorporate replication in your experiment? How much replication will you have?
(e) How will you incorporate randomization in your experiment? Be specific about how you will
randomize when conducting the experiment.
Before you actually begin to conduct the experiment, check with Ellis or me.
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(f) Conduct the experiment you have designed. Record your data points on the group answer sheet.
(g) Take your data and complete a regression analysis using JMP. Print off the output and use it to
answer the following questions.
i. Describe the relationship between the weight of the bag of M&Ms and the number of M&Ms.
What is the value of the correlation coefficient?
ii. What is the least squares regression equation?
iii. What is the value and interpretation of the slope of the regression equation?
iv. What is the value and interpretation of the intercept of the regression equation? Does this
seem correct? Explain briefly.
v. What is the value and interpretation of R2 for this regression? How good is the prediction of
the weight of the bag and contents using the number of M&Ms?
vi. Describe the plot of residuals. What does this tell you about the adequacy of the linear model
to approximate the general trend between number and weight?
vii. What is your estimate of the average weight of one M&M based on the regression analysis?
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Statistics 101: Section L - Laboratory 7
Group Answer Sheet
Names of Group Members:
1. Group Activity 1:
(a) Response Variable
(b) Treatments
(c) Experimental Units
(d) Outside Variables and Control
(e) Replication
(f) Practical Considerations
(g) Randomization
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2. Group Activity 2:
(a) Response Variable
(b) Explanatory Variable and Treatments
(c) Outside Variables and Control
(d) Replication
(e) Randomization
(f) Data
Explanatory
Response
Explanatory
Response
Explanatory
Response
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