A gender-selection technique is designed to increase the likelihood that a baby
ID: 2927448 • Letter: A
Question
A gender-selection technique is designed to increase the likelihood that a baby will be a girl. In the results of the gender-selection technique,
965
births consisted of
497
baby girls and
468
baby boys. In analyzing these results, assume that boys and girls are equally likely.
a. Find the probability of getting exactly
497
girls in
965
births.
b. Find the probability of getting
497
or more girls in
965
births. If boys and girls are equally likely, is
497
girls in
965
births unusually high?
c. Which probability is relevant for trying to determine whether the technique is effective: the result from part (a) or the result from part (b)?
d. Based on the results, does it appear that the gender-selection technique is effective?
Explanation / Answer
Sample proportion of girls p = 497/965 = 0.515
a) Using Binomial distribution, n = 956, x= 497
the probability of getting exactly 497 girls in 965 births.
In Excel,
=BINOM.DIST(497,965,0.515,FALSE)
Answer: 0.025689721
b) the probability of getting 497 or more girls in 965 births.
In Excel,
=1-BINOM.DIST(496,965,0.515,TRUE)
Answer: 0.512331181
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