If there is no seasonal effect on human births, we would expect equal numbers of
ID: 3050815 • Letter: I
Question
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, 29 were born in winter, 36 in spring, 31 in summer, and 24 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?
-The expected number of births in each season if there is no "seasonal effect" is
b) Compute the 2 statistic.
- 2= ____?
c) How many degrees of freedom does the 2 statistic have?
-df= ___?
Explanation / Answer
a) the Expected frequency 'E'= [29+36+31+24]/4 = 30
b) Chi square test statistic = 2 = [ (Oi - Ei)2 / Ei ]
The Chi^2 value is: 4.667
X^2 (29-30)^2+(36-30)^2+(31-30)^2+(24-30)^2/30 = 74/30 = 2.466
The Chi^2 value is 2.466. . The result is not significant at p=0.05.
c) the degrees of freedom = n - 1 = 4 - 1 = 3