Unnithan, Houser, and Fernhall (2006) were interested in whether playing the game Dance Dance Revolution (DDR) affected the heart rate of overweight and nonoverweight adolescents differently. A group of 22 adolescents, 10 classified as overweight and 12 as not overweight, played DDR for 12 minutes, during which time the researchers measured each participant's heart rate. Which statistical test should the researchers use to analyze their data?
a) independent-samples t test
b) dependent-samples t test
c) z test
d) single-sample t test