UFO Sighters' Personalities (cont.)

Reconsider the study described in Activity 21-7, (part of the data from which you analyzed in Activity 24-11.) A control group of 53 community members (who had not reported UFO experiences) had a mean IQ of 100.6 with a standard deviation of 12.3. Use this information together with that presented in Activity 24-11 to test whether the mean IQ's of community members and UFO sighters differ significantly. Show the details of the test and write a one-sentence conclusion. Also find a confidence interval for the difference in population means and explain what the interval reveals.

Activity 24-11

Consider the study described in Activity 21-7 dealing with individuals who claim to have had experiences with UFO's. The sample mean IQ of the 25 people in the study who claimed to have had an intense experience with a UFO was 101.6; the standard deviation of these IQ's was 8.9.

(a) Use this sample information to produce a 95% confidence interval for the population mean IQ of all people who have had intense UFO expenences.

(b) Conduct a test of significance for assessing whether the sample data support the belief that the mean IQ among all people who have had intense UFO experiences exceeds 100. Write a one-sentence conclusion as well as reporting the details of the test.

Activity 21-7

In a 1993 study, researchers took a sample of people who claimed to have had an intense experience with an unidentified flying object (UFO) and a sample of people who did not claim to have had such an experience. They then compared the two groups on a wide variety of variables, including IQ. The sample mean IQ of the UFO group was 101.6 and that of the control group was 100.6.

Is this study a controlled experiment or an observational study? If it is an observational study, what kind is it? Explain your answers.