Conducting a Chi-Square Test for Goodness of Fit — Quiz
Question 7 • Statistics
A doctor used to believe that babies were equally likely to be born any day of the week, but with the rise in scheduled deliveries, the doctor now claims that babies are twice as likely to be born on a weekday (Monday through Friday) than on a weekend (Saturday and Sunday). To test this theory, she selects a random sample of 120 babies born this year and determines on which day of the week they were born. She would like to carry out a test of significance to test her claim. Are the conditions for inference met?
Answer
A
Yes, all of the conditions for inference are met.
B
No, the Large Counts condition is not met.
C
No, the random condition is not met.
D
No, the 10 percent condition is not met.
Explanation
The random sample meets the random condition. Under the doctor’s claim, the probability of a weekday birth is 2/3 and of a weekend birth is 1/3, so the expected counts in 120 births are 120(2/3) = 80 weekdays and 120(1/3) = 40 weekend births. Both expected counts are at least 10, so the Large Counts condition is met. A sample of 120 is also less than 10% of the births this year, so the 10 percent condition is met.
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