State whether the investigator should use independent samples, repeated measures, or matched samples:

a. An investigator wants to know if parental marital status is related to children’s reading achievement. She draws a sample of children from single-parent homes and a sample of children from married-parent homes. She compares the tested reading achievement levels of both groups.

b. An investigator wants to know if parental marital status is related to children’s reading achievement. She also thinks that parental marital status may determine socioeconomic level, which in turn may affect children’s reading level. Therefore, she draws a sample of children from single-parent homes and a sample of children from married-parent homes, being careful to draw equal numbers of children from high, middle, and low socioeconomic strata within the married- and single-parent groups. She compares the tested reading achievement levels of both groups.