3.56 What is needed?

Explain what is deficient in each of the following proposed experiments, and explain how you would improve the experiment.

3.57 What is wrong?

Explain what is wrong with each of the following randomization procedures, and describe how you would do the randomization correctly.

3.58 Evaluate a new method for training new employees.

A new method for training new employees is to be evaluated by randomly assigning new employees to either the current training program or the new method. A questionnaire will be used to evaluate the satisfaction of the new employees with the training. Explain how this experiment should be done in a double-blind fashion.

3.59 Can you change attitudes of workers about teamwork?

You will conduct an experiment designed to change attitudes of workers about teamwork. Discuss some variables that you might use if you were to use a block design for this experiment.

3.60 An experiment for a new product.

Compost tea is rich in microorganisms that help plants grow. It is made by soaking compost in water.²⁵ Design a comparative experiment that will provide evidence about whether or not compost tea works for a particular type of plant that interests you. Be sure to provide all details regarding your experiment, including the response variable or variables that you will measure. Assuming that the experiment shows positive results, write a short description about how you would use the results in a marketing campaign for compost tea.

3.61 Marketing your training materials.

Water quality of streams and lakes is an issue of concern to the public. Although trained professionals typically are used to take reliable measurements, many volunteer groups are gathering and distributing information based on data that they collect.²⁶ You are part of a team to train volunteers to collect accurate water quality data. Design an experiment to evaluate the effectiveness of the training. Write a summary of your proposed design to present to your team. Be sure to include all the details that they will need to evaluate your proposal. How would you use the results of the experiment to market your training materials?

3.62 Randomly assign the subjects.

You can use the Simple Random Sample applet to choose a treatment group at random once you have labeled the subjects. Example 3.22 (page 151) describes an experiment in which 20 students are chosen from a group of 40 for the treatment group in a study of the effect of cell phones on driving. Use the applet to choose the 20 students for the experimental group. Which students did you choose? The remaining 20 students make up the control group.

3.63 Randomly assign the subjects.

The Simple Random Sample applet allows you to randomly assign experimental units to more than two groups without difficulty. Example 3.23 (page 152) describes a randomized comparative experiment in which 150 students are randomly assigned to six groups of 25.

3.64 Random digits.

Table B is a table of random digits. Which of the following statements are true of a table of random digits, and which are false? Explain your answers.

3.65 I’ll have a Mocha Light.

Here’s the opening of a press release: “Starbucks Corp. on Monday said it would roll out a line of blended coffee drinks intended to tap into the growing popularity of reduced-calorie and reduced-fat menu choices for Americans.” You wonder if Starbucks customers like the new “Mocha Frappuccino Light” as well as the regular version of this drink.

3.66 Price cuts on athletic shoes.

Stores advertise price reductions to attract customers. What type of price cut is most attractive? Market researchers prepared ads for athletic shoes announcing different levels of discounts (20%, 40%, or 60%). The student subjects who read the ads were also given “inside information” about the fraction of shoes on sale (50% or 100%). Each subject then rated the attractiveness of the sale on a scale of 1 to 7.

3.67 Effects of price promotions.

A researcher is studying the effect of price promotions on consumers’ expectations. She makes up a history of the store price of a hypothetical brand of laundry detergent for the past year. Students in a marketing course view the price history on a computer. Some students see a steady price, while others see regular promotions that temporarily cut the price. Then the students are asked what price they would expect to pay for the detergent.

3.68 Aspirin and heart attacks.

“Nearly five decades of research now link aspirin to the prevention of stroke and heart attacks.” So says the Bayer Aspirin website, bayeraspirin.com. The most important evidence for this claim comes from the Physicians’ Health Study, a large medical experiment involving 22,000 male physicians. One group of about 11,000 physicians took an aspirin every second day, while the rest took a placebo. After several years, the study found that subjects in the aspirin group had significantly fewer heart attacks than subjects in the placebo group.

3.69 Marketing to children.

If children are given more choices within a class of products, will they tend to prefer that product to a competing product that offers fewer choices? Marketers want to know. An experiment prepared three sets of beverages. Set 1 contained two milk drinks and two fruit drinks. Set 2 had two fruit drinks and four milk drinks. Set 3 contained four fruit drinks but only two milk drinks. The researchers divided 120 children aged 4 to 12 years into three groups at random. They offered each group one of the sets. As each child chose a beverage to drink from the set presented, the researchers noted whether the choice was a milk drink or a fruit drink.

3.70 Effects of TV advertising.

You decide to use a completely randomized design in the two-factor experiment on response to advertising described in Example 3.16 (page 143). The 30 students named below will serve as subjects. Outline the design. Then use software or Table B at line 110 to randomly assign the subjects to the six treatments.

3.71 Temperature and work performance.

An expert on worker performance is interested in the effect of room temperature on the performance of tasks requiring manual dexterity. She chooses temperatures of 20°C (68°F) and 30°C (86°F) as treatments. The response variable is the number of correct insertions, during a 30-minute period, in a peg-and-hole apparatus that requires the use of both hands simultaneously. Each subject is trained on the apparatus and is then asked to make as many insertions as possible in 30 minutes of continuous effort.