Question

1. the manager of a public swimming pool wants to compare the effectiveness of two laundry detergents, detergent a and detergent b, in cleaning the towels used daily. as each dirty towel is turned in, it is placed into the holding area on the premises. when the washing machine contains 70 towels, the manager randomly determines whether detergent a or detergent b will be used for that load. after washing, each towel in the load of towels is rated on a scale of 1 to 15 by a person who does not know which detergent was used. the manager continues this experiment for many days. which of the following best describes the managers study? a. an observational study b. a randomized block design with detergent a and detergent b as blocks c. a randomized block design with the washing machine as the block d. a matched - pairs design with detergent a and detergent b as the pair e. a completely randomized design 2. a randomized block design will be used in an experiment to compare two lotions that protect people from getting sunburned. which of the following should guide the formation of the blocks? a. participants in the same block should receive the same lotion b. participants should be kept blind as to which block they are in. c. participants within each block should be as similar as possible with respect to how easily they get sunburned. d. participants should be randomly assigned to the blocks. e. participants within each block should be as different as possible with respect to how easily they get sunburned. 3. a medical researcher is interested in assessing the effectiveness of a new medication for pain relief. three hundred volunteers will be randomly assigned to groups. one group will receive the new medication at a low dose, one group will receive the new medication at a high dose, and one group will receive a placebo that looks like the new medication but does not contain any active ingredients. each person will be asked to rate his or her level of pain at the beginning of the experiment and again two hours after taking the medication or placebo. what is the number of treatments for this experiment? a. 2 b. 3 c. 6 d. 100 e. 300

Explanation:

1.

In a completely - randomized design, treatments (in this case, Detergent A and Detergent B) are randomly assigned to experimental units (loads of towels). There is no blocking involved as described for the other options. The manager is randomly choosing which detergent to use for each load of 20 towels.

In a randomized block design, the goal of forming blocks is to group together experimental units that are similar with respect to a factor that could affect the response variable. Here, the response variable is related to getting sunburned, so participants within each block should be as similar as possible with respect to how easily they get sunburned.

The treatments in an experiment are the different conditions being imposed on the experimental units. Here, the treatments are the new medication at a low - dose, the new medication at a high - dose, and the placebo. So there are 3 treatments.

Answer:

e. A completely randomized design

2.