The mean weight of newborn infants at a community hospital is said to be 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. What is the sample variance?
A) 1.177
B) 6.6
C) 1.385
D) 7.6

Question

Quizplus · Accepted Answer

Step 1: Find the sample mean
x̄ = (9.0 + 7.3 + 6.0 + 8.8 + 6.8 + 8.4 + 6.6) / 7 = 7.6

Step 2: Calculate the sample variance
s^2 = [(9.0 - 7.6)^2 + (7.3 - 7.6)^2 + (6.0 - 7.6)^2 + (8.8 - 7.6)^2 + (6.8 - 7.6)^2 + (8.4 - 7.6)^2 + (6.6 - 7.6)^2] / 6
s^2 = 1.385

Therefore, the sample variance is 1.385, which corresponds to choice C.

The Mean Weight of Newborn Infants at a Community Hospital