8.66 Birth Order and University Success In a study of the relationship between birth order and university success, an investigator found that 126 in a sample of 180 university graduates were firstborn or only children. In a sample of 100 non-graduates of comparable age and socioeconomic background, the number of firstborn or only children was 54. Estimate the difference between the proportions of firstborn or only children in the two populations from which these samples were drawn. Use a 90% confidence interval and interpret your results.