Placebo Effect A recent study investigated potential effects of a sham acupunctu
ID: 2948454 • Letter: P
Question
Placebo Effect A recent study investigated potential effects of a sham acupuncture placebo (Kaptchuk et al., 2008). Patients who suffer from irritable bowel syndrome were randomly assigned to one of three groups: a baseline group that received no treatment, a group that received sham acupuncture but minimal interaction with a practitioner, and a group that received substantial interaction with a practitioner in addition to sham acupuncture. At the end of six weeks, researchers noted whether or not the patient experienced adequate relief of symptoms. The following table reveals the resuilts: Placebo Placebo Minimal Substantial Baseline Interaction Interaction Experienced Adequate Relief Did Not Experience Adequate Relief Total 27 38 50 50 32 71 82 a. Is this an observational study or an experiment? This is an b. For each group, calculate the proportion who experienced adequate relief of symptoms Round your answers to three decimal places Placebo with Minimal Interaction Placebo with Substantial Interaction Baseline Experienced Adequate Relief Did Not Experience Adequate Relief c. Conduct the appropriate test of whether these three proportions differ significantly. Round the test statistic to three decimal places. Use the chi-square distribution table to find a range for the p -value. If there is no lower limit on the p-value, enter 0 for the lower limit. If there is no upper limit on the p-value, enter i for the upper limit. Ho: The population proportions who would experience adequate relief of symptoms of the three treatment groups Ha: The population proportions who would experience adequate relief of symptoms of the three treatment groups for each for each Technical conditions: The test statistic is X2 =Explanation / Answer
(a) Experiment
The researcher has no control over the variables in an observational study. An experiment is a method of applying treatments to a group and recording the effects. Remember, a good group experiment will have two basic elements: a control and a treatment.
(b)
(c) H0: The population proportions who would experience adequate relief of symptoms equal for each of the three treatment gropus
Ha:The population proportions who would experience adequate relief of symptoms unequal for each of the three treatment gropus
if chi-square>5.99, we reject H0
the test statistic is chi-square=sum((O-E)2/E)=11.17
P-value=0.0037
0.001<P-value<0.005
Baseline Placebo with Minimial interaction Placebo with substantial interaction Experienced Adequate Relief 0.117 0.165 0.217 Did not Experienced Adequate Relief 0.217 0.143 0.139