I am working on an assignment for school. This is all my work. Does my math add up? If not, can you please fix it?

For an accurate result, 12 male participants and 12 female participants were needed. In this research study, we used stratified sampling and convenience sampling to evaluate the participants. The participants were recruited after completing a survey. Then, they were randomly selected. Participants were asked to participate in a study for an experimental psychology class. If the participant refused, then he or she was thanked and not bothered further. If the participant agreed, then he or she was required to sign an informed consent. If the participant was reluctant, then they were excluded from the research study. Participants completed the experiment one at a time. It is predicted that 25% of the males will be between the ages of 20 - 25, 25% of the males will be between the ages of 26 - 31, 25% of the males will be Caucasian, and 25% of the males will be African American. It is predicted that 25% of the females will be between the ages of 20 - 25, 25% of the females will be between the ages of 26 - 31, 25% of the females will be Caucasian, 25% of the females will be African American.