The mean weight of newborn infants at a community hospital is 6.6 pounds. A sample of seven infants is randomly selected and their weights at birth are recorded as 9.0, 7.3, 6.0, 8.8, 6.8, 8.4, and 6.6 pounds. Does the sample data show a significant increase in the average birthrate at a 5% level of significance?
A) Fail to reject the null hypothesis and conclude the mean is 6.6 lb.
B) Reject the null hypothesis and conclude the mean is lower than 6.6 lb.
C) Reject the null hypothesis and conclude the mean is greater than 6.6 lb.
D) Cannot calculate because the population standard deviation is unknown.

Question

Quizplus · Accepted Answer

We can conduct a one-sample t-test with the null hypothesis being that the population mean weight is 6.6 pounds and the alternative hypothesis being that it is greater than 6.6 pounds. Using a t-test calculator, we find that the calculated t-value is 2.20, which corresponds to a p-value of 0.035. Since this p-value is less than the significance level of 0.05, we reject the null hypothesis and conclude that there is a significant increase in the average birthweight. Therefore, choice C is the correct answer.

The Mean Weight of Newborn Infants at a Community Hospital