Question

In a study reported in the September 24, 2007, issue of the Archives of Internal Medicine, German researchers described a study conducted on 1162 German adults suffering from chronic low-back pain. These subjects were randomly assigned to one of three groups: real acupuncture, sham acupuncture, and conventional therapy. Researchers found that 47% of subjects in the real acupuncture group improved, compared to 44% in the sham acupuncture group and 27% in the conventional therapy group.

a. Identify the observational units in this study

b. Identify the explanatory variable

b.i. Is the explanatory quantitative, categorical or binary?

c. Identify the response variable

c.i. Is the response variable quantitative, categorical, or binary?

d. Is this an observational study or an experiment? Explain briefly.

e. Did this study make use of random assignment or random sampling, or both, or neither? Explain briefly.

h. If the researchers find that the difference in improvement percentages between the real acupuncture group and the conventional therapy group is significant, would it be appropriate to conclude that real acupuncture causes a higher improvement rate than conventional therapy? Explain based on whether the study is an observational study or an experiment.

Answer 1

a. Observational units=1162 German adults suffering from chronic low-back pain

b. Explanatory variable, x_ij define as

xij=1 if Subject j is assigned to ith group; where i=1,2,3

=0 otherwise

where 1=real acupuncture

2=sham acupuncture

3=conventional therapy

The explanatory variable is categorical or binary

c. Response variable Y_ij defined as

Y_ij=1 if Subject j is improved when group i is applied

=0 otherwise

Hence response variable is categorical or binary.

d. This is an experimental study since  the researchers introduce three groups (real acupuncture, sham acupuncture, and conventional therapy) and study the effects of these groups.

e.  Since 1162 German adults suffering from chronic low-back pain were randomly assigned to one of three groups: real acupuncture, sham acupuncture, and conventional therapy so this study makes use of random assignment.

h. Yes, it is an experimental study and the difference in improvement percentages between the real acupuncture group and the conventional therapy group is significant so it is appropriate to conclude that real acupuncture causes a higher improvement rate than conventional therapy.