There were 562,157 live births in California in 2006; information about each of these births was arranged in alphabetical order using the mother’s name. State whether each of the following sampling procedures is likely to produced biased estimates of the average age of these mothers.

a. A random number generator was used to select 100 numbers between 1 and 562,157.

b. A random number generator was used to select 200 numbers between 1 and 562,157;

every other number was then discarded, leaving 100 numbers.

c. A random number generator was used to select 200 numbers between 1 and 562,157;

among the 200 mothers selected, the 50 youngest mothers and the 50 oldest mothers were discarded.