Answer
a) 0 percent
b) Unusually high
c) Part b)
d) Yes
Work Step by Step
a) The results of getting a girl is usually 50 percent. Thus, we find:
$\mu=np=(945)(.5)=472.5$
$ \sigma=\sqrt{npq}=\sqrt{(945)(.5)(.5)}=15.37$
Thus, we find z:
$z=\frac{878.5-472.5}{15.37}=26.41$
$z=\frac{879.5-472.5}{15.37}=26.47$
Thus, using the table of z-scores, we find that this corresponds to a probability of $.0000\ percent$
b) $z=\frac{878.5-472.5}{15.37}=26.41$
Thus, using the table of z-scores, we find that this corresponds to a probability of $.0001 \ percent$
Since the probability is so small that it is nearly 0 percent, this number is unusually high.
c) Part b) is more useful, for we do not care about getting exactly 845 girls; rather, we care whether or not 845 or more is a large number.
d) Yes, it is, for the odds of getting this high of a number by chance is almost 0.
