Assessment 4.2: Experiments 1. [4 points] The customer service call center for a major electronics manufacturer is trying to determine how
to keep customers who are on hold as happy as possible. They want to examine whether the type of music
they play while customers are on hold and whether or not there is a periodically-repeated recorded
message ("Thank you for your patience, we'll be with you as soon as possible.") have an impact on customer
satisfaction. They plan to randomly select customers who are on hold and play one of three different types
of music ("smooth jazz, classical, or Broadway show tunes) and either play recorded messages or not. After
the entire call is over, they will ask the customers to rate their overall customer service experience.
a. Suppose the company plans to conduct a completely randomized design. List the experimental
units, and all of the treatments in this experimental design.
b. Suppose the company is concerned that the time when the call is made (daytime versus evening)
will have an impact on which combination of music and messages is most effective. How might they
alter the design of this experiment to take this into account?
2. [3 points] Many utility companies have introduced programs to encourage energy conservation among
their customers. An electric company considers placing electronic meters in households to show what the
cost would be if the electricity use at that moment continued for a month. It gives these meters to 100 of its
customers for a year and then compares the average electricity use in these customers' homes this year to
the previous year. Result: These customers' average electricity use decreased by 10%. Explain why this is
not strong evidence that the use of the electronic meters caused customers to decrease their electricity use.
3. [3 points] Agricultural scientists for a chemical company want to determine if a newly developed fertilizer
produces heavier tomatoes than the fertilizer they currently manufacture. For their first pilot study, they
have 24 healthy young tomato plants growing in individual pots, numbered from 1 to 24. Describe the
design of a completely randomized, controlled experiment to test whether the new fertilizer produces
heavier tomatoes. Your answer should address all four basic principles of experimental design, and can be
written as a narrative or as a flow chart.