In Born together-Reared apart: the Landmark Minnesota twin study (2012), Nancy Segal discusses the efforts of research psychologists at the University of Minnesota to understand similarities and differences between twins by studying sets of twins who were raised separately. Below are critical reading SAT scores for several pairs of identical twins (twins who share all of their genes), one of whom was raised in a family with no other children (no siblings) and one of whom was raised in a family with other children (with siblings).

a. What is the mean difference between the critical reading SAT scores for the twins raised with no siblings and the twins raised with siblings?
b. Provide a 90% confidence interval estimate of the mean difference between the critical reading SAT scores for the twins raised with no siblings and the twins raised with siblings.
c. Conduct a hypothesis test of equality of the critical reading SAT scores for the twins raised with no siblings and the twins raised with siblings at a = .01. What is your conclusion?

With Siblings No Siblings SAT Score Name Donald Ronald Kedriana Kevin Erin Michael Josephine Jasmine Kraig Bernadette SAT Score Name Bob Matthew Shannon Tyler Michelle 420 610 590 390 410 430 510 620 510 680 580 610 510 630 570 630 530 590 500 610 630 430 460 490 460 Wilhelmina Donn Drew Lucinda Barry ulie Hannah 460 650 450 Larry Jennifer Diedra Latishia Bart Kara Rachel Joey Drew 460 580 490 Garrett 560 610 520 Nancy Simon Megan