Dr. Mandell wanted to know if IQ scores differed between participants in young adulthood and late adulthood. He gave 28 participants an IQ test, 13 in the young adulthood group and 15 in the late adulthood group, and then compared mean IQ scores for the groups. He hypothesized that there would be a statistically significant age difference in IQ scores. Contrary to Dr. Mandell's hypothesis, there were no differences in IQ scores between age groups in his study. Which test did Dr. Mandell most likely use to test his hypothesis? O Repeated-measures t test O Independent-samples t test O Single-sample t test O z-Test