Two independent groups

These individuals were selected from a larger set of names using random numbers. Those with the highest 12 random numbers were chosen for Group 2 and those 12 with the lowest random numbers were selected for Group 1.

NOTE the different characteristics of the two groups (i.e., regarding Class, Gender, and GPA). For example, there are more high GPA students in Group 1. Such variation occurs by chance. The statistical analysis will take that chance into account.

Group 1					Group 2
Student	Class	GPA	Gender		Student	Class	GPA	Gender
Person_43	Soph	High	M		Person_55	Soph	High	M
Person_8	Frosh	Middle	F		Person_26	Junior	Middle	F
Person_61	Senior	High	M		Person_24	Frosh	Low	F
Person_68	Frosh	Middle	F		Person_54	Junior	Low	F
Person_16	Frosh	High	F		Person_17	Senior	Middle	M
Person_18	Junior	Low	F		Person_46	Junior	High	F
Person_34	Junior	High	F		Person_57	Senior	Low	M
Person_62	Junior	Middle	F		Person_2	Junior	Middle	F
Person_49	Senior	High	M		Person_27	Soph	Low	M
Person_41	Senior	Middle	M		Person_67	Soph	High	M
Person_38	Junior	Middle	F		Person_44	Frosh	Middle	F
Person_60	Frosh	Low	F		Person_47	Soph	Middle	M

Matched groups (paired samples)

All the individuals were given random numbers. The 12 with the lowest random numbers were selected for Group 1. Then a matched group (Group 2) was selected by taking the next person who had the same characteristics as each person in Group 1.

NOTE that there are the same number of students with the various characteristics (e.g., 1 high GPA, Female Freshman, and 1 high GPA Male Sophomore) in each group. That is what makes them "matched groups" or "paired samples."

Group 1					Group 2 (matched)
Student	Class	GPA	Gender		Student	Class	GPA	Gender
Person_28	Frosh	High	F		Person_64	Frosh	High	F
Person_48	Frosh	Low	F		Person_36	Frosh	Low	F
Person_56	Frosh	Middle	F		Person_32	Frosh	Middle	F
Person_20	Frosh	Middle	F		Person_44	Frosh	Middle	F
Person_66	Junior	Low	F		Person_12	Frosh	Low	F
Person_42	Junior	Low	F		Person_72	Frosh	Low	F
Person_33	Senior	Low	M		Person_69	Senior	Low	M
Person_53	Senior	Middle	M		Person_29	Senior	Middle	M
Person_7	Soph	High	M		Person_31	Soph	High	M
Person_39	Soph	Low	M		Person_15	Soph	Low	M
Person_3	Soph	Low	M		Person_63	Soph	Low	M
Person_51	Soph	Low	M		Person_27	Soph	Low	M

Using matched groups (paired samples) provides a more powerful (sensitive) test because it controls for individual differences that might be affecting the outcome. The samples are made as much alike as possible (except for the treatment).

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