For each of the following excerpts, indicate whether the sample is biased or unbiased and explain why. If you answer "not sure" to an item, describe the additional information you would like to have before making a choice.

p.78 1. Researchers state, "To help resolve the questions posed above [in this research report), a telephone survey of 1,000 California residents was conducted... using random digit dialing (RDD). Sampling by means of RDD avoids the threat of systematically excluding that portion of the population with unlisted telephone numbers. "1 2. Researchers state, "For the analyses, we used a sample of Norwegian 13-year-old students (N = 1,736; 49% were girls) and 15-year-old students (N = 1,622; 51% were girls). The students were selected using a stratified, systematic sampling procedure, thus yielding a nationally representative sample. The sampling unit was the school class 2 3. Researchers state, "A total of 102 U.S. and 112 Japanese men participated in this study. The U.S. participants were recruited from an undergraduate student research pool in the psychology and educational psychology departments at a large public university in the Rocky Mountain region of the United States." 4. Researchers state, "A sample of 60 was randomly selected from 125 people arrested on DWI offenses and referred by the county to a professional evaluator between May 2000 and December 2003.-4 5. Researchers state, "Smokers (defined as individuals smoking 10 or more cigarettes per day) were approached at various locations on or near the University of Pittsburgh campus. The sample (N=102) included 42 men and 60 women, with an average age of 27.78.5 6. Researchers state that "Participants were 307 students in a convenience sample of volunteers in 18 elementary and middle school classes. After we accounted for missing data, including student absences from school during 1 or more days of the intervention, the actual sample size for the statistical analysis was 268.6 7. Researchers state that "Briefly, a stratified random sample of 4,907 coronary artery disease patients undergoing an angiogram at one... New York State hospital... was selected for the medical records abstraction portion of the study."2 8. Researchers state that "We commissioned Survey Sampling Incorporated to provide a random sample of 1,000 Florida residents of the initial sample members, 198 had moved, had incorrect addresses, were deceased, or were otherwise unreachable. These individuals were replaced with additional randomly selected residents. Thirty-three of the replacements also could not be contacted but were not replaced. Thus, the total number... was reduced to 967.8 0.79 2 9. Researchers state that "a standardized questionnaire developed for use in this study was mailed to a stratified random sample of 750 hospitals drawn from the American Hospital Association membership list. Hospitals were stratified according to size, geographic location, and stage of managed care development. 10. Researchers state. "A randomized sample of 2,400 surveys was sent to clinical psychology (n = 1,200) and clinical social work (n = 1,200) clinicians from all 50 U.S. states. Of those 2,400 surveys, 711 were returned with usable data, for a response rate of 29.6%.-10 11. Researchers state, "Participants were 230 first-year university students who responded to signs posted on campus or agreed to participate after being approached individually. Participation was anonymous and participants were paid $10.11 12. Researchers state, "Participants in Study 1 had been randomly selected from the membership lists of a large HMO. Because the focus of the research was on marital conflict, families were eligible only if they were intact (parents still living togetherl.12 13. Researchers state, "Participants were 3,446 Internet users... who had been involved in a close relationship. Each participant volunteered to complete an online questionnaire about their dating history at a Web site that features several psychological surveys. 14. Researchers state, "School guidance personnel selected a representative set of classrooms, taking into account grade level and academic difficulty. *14