In this chapter, we introduced you to three different independent groups designs: (a) random groups, (b) matched groups, and (c) natural groups. Below are five brief descriptions of research procedures. Read each description carefully and identify which type of independent groups design is illustrated.

1		A researcher asks for volunteers from a large psychology lecture class to participate in a psychology experiment involving two groups. He obtains 30 volunteers. Each person's name is put on an index card. The cards are shuffled and put into two piles of 15. Students whose names are in the first pile are placed in the experimental group and those in the other pile are assigned to the control group. random groups matched groups natural groups
2		A researcher wishes to test a hypothesis about transfer of physical abilities between professional sports. Specifically, she believes professional football players will have more difficulty hitting a baseball than will professional basketball players. From the rosters of two local professional teams she randomly selects 10 football players and 10 basketball players to compete in a baseball hitting contest. random groups matched groups natural groups
3		A psychologist assigns 60 male schizophrenics to five different psychotherapy treatment groups. Only males who are under 60 years of age, have been on medication less than 10 years, and who are in good physical health are included in the study. Once the 60 patients are identified, they are assigned to treatment groups by using a random numbers table. random groups matched groups natural groups
4		Twenty students with deficient study skills are assigned to two different training programs. Prior to assigning the students to the treatment groups, a vocabulary test is given to all 20 students. Students with similar vocabulary test scores are paired and then members of each pair are randomly assigned to either the first or second treatment condition. random groups matched groups natural groups
5		A researcher wishes to test the spelling abilities of 5th grade children from city and suburban schools. One hundred children from city schools and 100 children from suburban schools are randomly selected. Standardized test scores in the files of the students are used to find pairs of students (one from a city school and one from a suburban school) who have nearly identical reading comprehension scores. The investigator obtains 50 pairs of children in this way. The 50 children from the city schools and the 50 children from the suburban schools are then given a specially prepared spelling test. random groups matched groups natural groups