High School

A hypothesis regarding the weight of newborn infants at a community hospital is that the mean is 10.1 pounds. A sample of seven infants is randomly selected, and their weights at birth are recorded as 9.1, 12.1, 13.1, 14.1, 10.1, 15.1, and 16.1 pounds.

What is the sample variance?

Answer :

The sample variance for the given set of weights is approximately 6.5734 pounds squared.

To calculate the sample variance, you can follow these steps:

Step 1: Find the mean of the sample weights.

Add up the weights of the seven infants and divide by the number of infants (which is 7 in this case):

9.1 + 12.1 + 13.1 + 14.1 + 10.1 + 15.1 + 16.1 = 89.7

Mean = 89.7 / 7 = 12.8143 (rounded to four decimal places)

Step 2: Calculate the deviation of each weight from the mean.

Subtract the mean (12.8143) from each weight to get the deviation:

9.1 - 12.8143 = -3.7143

12.1 - 12.8143 = -0.7143

13.1 - 12.8143 = 0.2857

14.1 - 12.8143 = 1.2857

10.1 - 12.8143 = -2.7143

15.1 - 12.8143 = 2.2857

16.1 - 12.8143 = 3.2857

Step 3: Square each deviation.

Square each of the deviations calculated in Step 2:

(-3.7143)^2 = 13.7953

(-0.7143)^2 = 0.5102

(0.2857)^2 = 0.0816

(1.2857)^2 = 1.6541

(-2.7143)^2 = 7.3716

(2.2857)^2 = 5.2245

(3.2857)^2 = 10.8031

Step 4: Sum up the squared deviations.

Add up all the squared deviations:

13.7953 + 0.5102 + 0.0816 + 1.6541 + 7.3716 + 5.2245 + 10.8031 = 39.4404

Step 5: Calculate the sample variance.

Divide the sum of squared deviations by (n-1), where n is the number of observations (in this case, 7):

Sample Variance = 39.4404 / (7-1) = 6.5734 (rounded to four decimal places)

Therefore, the sample variance for the given set of weights is approximately 6.5734 pounds squared.

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