Gray E, Bortolozzi J
J Hered. 1977 Jul-Aug;68(4):241-4. doi: 10.1093/oxfordjournals.jhered.a108822.
During 1974--75, data on sex and family size were obtained from approximately 500 Brazilian college students and their parents. Sex ratios for the immediate and parental generations were 107:100 and 106:100, respectively. Correlation coefficients were calculated between sexes of various children in families of the immediate generation. A significant positive relationship was found between sexes of the first two children in families of two or more children. The overall correlation between sexes of successive births was positive but not significant. Correlation coefficients between sexes separated by one or more births were not significant. The observed frequencies of combinations of sexes within the various family sizes did not differ from expected frequencies. Average numbers of children per family were 4.39 and 6.80 for the immediate and parental generations, respectively. Average family sizes decreased as the formal educational level of the parents increased. If the parents' desired both sexes of children, such preferences had no measurable influence on family size.
在1974年至1975年期间，从大约500名巴西大学生及其父母那里获取了关于性别和家庭规模的数据。直系亲属一代和父母一代的性别比分别为107:100和106:100。计算了直系亲属一代家庭中不同孩子性别的相关系数。在两个或更多孩子的家庭中，头两个孩子的性别之间存在显著的正相关关系。连续出生孩子的性别总体相关性为正，但不显著。相隔一个或多个出生的孩子性别之间的相关系数不显著。不同家庭规模中性别组合的观察频率与预期频率没有差异。直系亲属一代和父母一代家庭的平均子女数分别为4.39和6.80。随着父母正规教育水平的提高，平均家庭规模减小。如果父母想要不同性别的孩子，这种偏好对家庭规模没有可衡量的影响。
