A study was conducted to investigate the relationship between maternal smoking during pregnancy and the presence of congenital malformations in the child. Among the children who suffer from an abnormality other than Down's syndrome or an oral cleft, 32.8% have mothers who smoked during pregnancy. This proportion is homogeneous for children with various types of defects.

a. If you were to select repeated samples of size 25 from this population, what could you say about the distribution of sample proportions? List three properties.

b. Among the samples of size 25, what fraction has a sample proportion of 0.45 or higher?

c. What fraction has a sample proportion of 0.20 or lower?

d. What proportion value cuts off the lower 10% of the distribution?