Identify Type 1 and Type II Errors
For the following four examples (A, B, C, and D) identify the given scenario as either a potential Type I or Type II error. Explain your decision by referring to the definitions of Type I and Type II errors.
A. Investigators are researching a new vaccine to prevent the onset of AIDS in HIV positive subjects. One hundred HIV positive subjects volunteered to participate. Half of the subjects (N=50) were randomly assigned to condition one, which received the experimental vaccine, while the other half (N=50) were assigned to condition, which received a placebo. Medically, the vaccine results looked very encouraging, but statistically significant differences between the groups were not obtained. The researchers failed to reject the null hypothesis (p is less .01) and the public is denied possible treatment.
B. Educational consultants were hired by a progressive California school district to study the effectiveness of competitive versus cooperative learning. The school district was known for its highly competitive philosophy, for which it was criticized despite it’s successful students’ test scores on the national assessment. The educational consultants researched several school districts nationwide and in Japan. They found that school districts that operated with a cooperative model had significantly higher test scores and higher student satisfaction than the competitive school (i.e., investigators rejected the null hypothesis). The competitive school district is strongly considering a bond measure in the next election to fund a change to the cooperative model with estimated cost of approximately 250 million dollars.
C. Silicon breast implants have been popular for many years for purposes of breast reconstruction and breast enlargement. Since no evidence had been collected by the drug manufacturing company nor the public, it was incorrectly assumed that they presented no harm to public health (i.e., failure to reject the null hypothesis). Currently, due to reports of serious complications from thousands of women who elected to have this surgery, silicon implants are no longer being produced by major drug manufacturers.
D. In the 1930’s surgical procedures in which the neural connection between the pre-frontal lobes was severed were performed frequently. Lobotomies were used on chronically hospitalized mental patients. It was considered a quick and easy treatment for mental disorders. The null hypothesis was incorrectly rejected. We now know that lobotomized patients may sink into a confused stupor or become vegetable-like. Today, lobotomies are rarely performed in psychological clinical practice.