About Experiment Design
19] Nurse practitioners are nurses with advanced qualications who often act much like primary care physicians. Are theyr as effective as doctors at treating patients with chronic conditions? An experiment was conducted with 1316 patients who had been diagnosed with asthma, diabetes, or high blood pressure. Within each condition, patients were randomly assigned to either a doctor or a nurse practitioner. The responSe variables included measures of the patients' health and of their satisfaction with their medical care after 6 months. a) Which are the blocks in this experiment: the different diagnoses (asthma, and so on] or the type ofcare (nurse or doctor]? I!) Explain why a randomized block design is preferable to a completely randomized design here. 1'7] What are the four principles of experimental design? a] : Use a design that compares two or more treatments b] : Use chance to assign experimental units to different treatments. c] : Keep other variables [besides the ones you are testing) that might affect the response of the subject the same for all groups. I!) : Use enough experimental units in each group so that any differences in the effects of the treatments can be distinguished from chance differences between groups 18] Researchers in Canada performed an experiment with university students to examine the effects of in-class laptop use on student learning. All participants in the study were rst year undergraduate students enrolled in in the business administration program. They were asked to attend a university- style lecture and take notes with their laptops. Half of the participants were assigned to complete other non-lecture related online tasks during the lecture. These tasks were meant to imitate typical student Web browsing during classes. The remaining students simply took notes with their laptops. To assign the treatments. the researchers printed 4-D papers with instructions [20 with multitasking and 20 without], shufed them. and handed them out at random to students in the classroom. At the end of the lecture. all participants took a comprehension test to measure how much they learned from it. The results: students who were assigned to multitask did signicantly worse [1 1%) than students who were not assigned to multitask. Explain how each of the four principles of experimental design was used in the multitasking study. Section 2.5 Experiment Design 14) Does reducing screen brightness increase battery life in laptop computers? To find out, researchers obtained 30 new laptops of the same brand. They chose 15 of the computers at random and adjusted their screens to the brightest setting. The other 15 laptop screens were left at the default setting - moderate brightness. Researchers then measured how long each machine's battery lasted. Was this an observational study or an experiment? 15) Does eating dinner with their families improve students' academic performance? According to an ABC News article, "Teenagers who eat with their families at least five times a week are more likely to get better grades in school. This finding was based on a sample survey conducted by researchers at Columbia University. Was this an observational study or an experiment? 16) A study published in the New England Journal of Medicine (March 11, 2010) compared two medicines to treat head lice: an oral medication called ivermectin and a topical lotion containing malathion. Researchers studied 376 households in areas around the world. Of the 185 households randomly assigned to ivermectin, 171 were free from head lice after 2 weeks compared with only 151 of the 191 households randomly assigned to malathion. a) Identify the experimental units b) What are the explanatory and response variables c) What are the treatments used
