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Find the sample variance and standard deviation for the following data set:
[tex]\[ 7, 53, 13, 51, 38, 23, 32, 30, 30, 27 \][/tex]

Choose the correct answer below. Fill in the answer box to complete your choice. (Round to two decimal places as needed.)

A. [tex]\(\sigma^2 =\)[/tex] [tex]\(\square\)[/tex]

B. [tex]\(s^2 = 212.49\)[/tex]

Choose the correct answer below. Fill in the answer box to complete your choice. (Round to one decimal place as needed.)

A. [tex]\(\sigma =\)[/tex] [tex]\(\square\)[/tex]

B. [tex]\(s =\)[/tex] [tex]\(\square\)[/tex]


Sagot :

Let's follow the steps to calculate the sample variance and the sample standard deviation for the given data set:
[tex]\[ 7, 53, 13, 51, 38, 23, 32, 30, 30, 27 \][/tex]

1. Calculate the mean (average) of the data:

[tex]\[ \text{Mean} \, (\bar{x}) = \frac{\sum x_i}{n} \][/tex]

where [tex]\(\sum x_i\)[/tex] is the sum of all the data points and [tex]\(n\)[/tex] is the number of data points.

[tex]\[ \bar{x} = \frac{7 + 53 + 13 + 51 + 38 + 23 + 32 + 30 + 30 + 27}{10} = \frac{304}{10} = 30.4 \][/tex]

2. Calculate the squared differences from the mean:

For each data point [tex]\(x_i\)[/tex], calculate [tex]\((x_i - \bar{x})^2\)[/tex]:

[tex]\[ \begin{align*} (7 - 30.4)^2 &= (-23.4)^2 = 547.56 \\ (53 - 30.4)^2 &= (22.6)^2 = 510.76 \\ (13 - 30.4)^2 &= (-17.4)^2 = 302.76 \\ (51 - 30.4)^2 &= (20.6)^2 = 424.36 \\ (38 - 30.4)^2 &= (7.6)^2 = 57.76 \\ (23 - 30.4)^2 &= (-7.4)^2 = 54.76 \\ (32 - 30.4)^2 &= (1.6)^2 = 2.56 \\ (30 - 30.4)^2 &= (-0.4)^2 = 0.16 \\ (30 - 30.4)^2 &= (-0.4)^2 = 0.16 \\ (27 - 30.4)^2 &= (-3.4)^2 = 11.56 \\ \end{align*} \][/tex]

3. Calculate the sample variance:

[tex]\[ s^2 = \frac{\sum (x_i - \bar{x})^2}{n - 1} \\ \][/tex]

[tex]\[ s^2 = \frac{547.56 + 510.76 + 302.76 + 424.36 + 57.76 + 54.76 + 2.56 + 0.16 + 0.16 + 11.56}{10 - 1} \\ s^2 = \frac{1912.4}{9} = 212.49 \\ \][/tex]

Thus, the sample variance is [tex]\(s^2 = 212.49\)[/tex].

4. Calculate the sample standard deviation:

[tex]\[ s = \sqrt{s^2} = \sqrt{212.49} \approx 14.6 \][/tex]

Thus, the sample standard deviation is [tex]\(s = 14.6\)[/tex].

With these calculations, we can fill in the boxes:
- For the sample variance:
[tex]\[ B. \boxed{s^2=212.49} \][/tex]

- For the sample standard deviation:
[tex]\[ B. \boxed{s=14.6} \][/tex]