SAT Mathematics Practice Test 2

When survey participants are selected at random from a larger population, the sample statistics calculated from the survey can be generalized to the larger population. Since 10 of 300 students surveyed at Lincoln School have 4 siblings, one can estimate that this same ratio holds for all 2,400 students at Lincoln School. Also, since 10 of 300 students surveyed at Washington School have 4 siblings, one can estimate that this same ratio holds for all 3,300 students at Washington School. Therefore, approximately

10

30

×2,400=80 students at Lincoln School and

10

30

×3,300=110 students at Washington School are expected to have 4 siblings. Thus, the total number of students with 4 siblings at Washington School is expected to be 110−80=30
Choices A, B, and D are incorrect and may result from either conceptual or calculation errors. For example, choice A is incorrect; even though there is the same ratio of survey participants from Lincoln School andWashington School with 4 siblings, the two schools have a different totalnumber of students, and thus, a different expected total number of studentswith 4 siblings.