Statistics

Section 2.4 – Assignment

1.  Explain why blinding is reasonable strategy in many experiments.

2.  Swedish researchers concluded that viewing and discussing art soothes the soul and helps relieve medical conditions such as high blood pressure and constipation. This conclusion was based on a study in which 20 elderly women gathered once a week to discuss different works of art. The study also included a control group of 20 elderly women who met once a week to discuss their hobbies and interests. At the end of 4 months, the art discussion group was found to have a more positive attitude, to have lower blood pressure, and to use fewer laxatives than the control group.

  1. Why would it be important to determine if the researchers assigned the women participating in the study at random to one of the two groups?
  2. Explain why you think that the researchers included a control group in this study.

3.  The article “Doctor Dogs Diagnose Cancer by Sniffing It Out” reports the results of an experiment described in the journal Integrative Cancer Therapies. In this experiment, dogs were trained to distinguish between people with breast and lung cancer and people without cancer by sniffing exhaled breath. Dogs were trained to lay down if they detected cancer in a breath sample. After training, dogs’ ability to detect cancer was tested using breath sample from people whose breath had not been using in training the dogs. The paper states, “The researchers blinded both the dog handlers and experimental observers to the identity of the breath samples.” Explain why this blinding is an important aspect of the design of this experiment.

4.  Researchers at the University of Pennsylvania suggest that a nasal spray derived from pheromones (chemicals emitted by animals when they are trying to attract a mate) may be beneficial in relieving symptoms of premenstrual syndrome (PMS).

  1. Describe how you might design an experiment using 100 female volunteers who suffer from PMS to determine whenterh the nasal spray reduces PMS symptoms.
  2. Does your design from Part (a) include a placebo treatment? Why or why not?
  3. Does your design from Part (a) involve blinding? Is it single blind or double blind? Explain.

5.  Pismo Beach, California, has an annual clam festival that includes a clam chowder contest. Judges rate clam chowders from local restaurants, and the judging is done in such a way that the judges are now aware of which chowder is from which restaurant. One year, much to the dismay of the seafood restaurants on the waterfront, Denny’s chowder was declared the winner! (When asked what the ingredients were, the cook at Denny’s said he wasn’t sure-he just had to add the right amount of nondairy creamer to the soup stock that he got from Denny’s distribution center!)

  1. Do you think that Denny’s chowder would have won the contest if the judging had not been blind? Explain.
  2. Although this was not an experiment, your answer to Part (a) helps to explain why those measuring the response in an experiment are often blinded. Using your answer in Part (a) explain why experiments are often blinded in this way.