Human births If there is no seasonal effect on human births, we would expect equal numbers of children to be born in each season (winter, spring, summer, and fall). A student takes a census of her statistics class and finds that of the 120 students in the class, 25 were born in winter, 35 in spring, 32 in summer, and 28 in fall. She wonders if the excess in the spring is an indication that births are not uniform throughout the year.
a) What is the expected number of births in each season if there is no “seasonal effect” on births?
b) Compute the x2
statistic.
c) How many degrees of freedom does the x2
statistic have?
Q22.:
Bank cards At a major credit card bank, the percentages of people who historically apply for the Silver, Gold, and Platinum cards are 60%, 30%, and 10%, respectively. In a recent sample of customers responding to a promotion, of 200 customers, 110 applied for Silver, 55 for Gold, and 35 for Platinum. Is there evidence to suggest that the percentages for this promotion may be different from the historical proportions?
a) What is the expected number of customers applying for each type of card in this sample if the historical proportions are still true?
b) Compute the x2
statistic.
c) How many degrees of freedom does the x2
statistic have?