A chemical company sells a specialized industrial lubricant in 20-liter containers. A random sample of the latest production lot shows the contents of 10 containers to be [tex]$20.3, 19.91, 19.98, 19.69, 19.54, 20.51, 20.36, 20.46, 19.68, 20.56$[/tex] liters. Find the standard deviation of the sampled containers' contents.

A. [tex]$\sigma = 0.55$[/tex]
B. [tex]$\sigma = 0.53$[/tex]
C. [tex]$\sigma = 0.36$[/tex]
D. [tex]$\sigma = 0.42$[/tex]



Answer :

To find the standard deviation of the sample containers' contents, we follow these steps:

1. Collect the sample data: The contents of the 10 containers are given as follows:
[tex]\[ 20.3, 19.91, 19.98, 19.69, 19.54, 20.51, 20.36, 20.46, 19.68, 20.56 \text{ liters} \][/tex]

2. Calculate the mean: The mean (average) of the sample contents is calculated by summing all the values and then dividing by the number of observations.
[tex]\[ \text{Mean} = \frac{20.3 + 19.91 + 19.98 + 19.69 + 19.54 + 20.51 + 20.36 + 20.46 + 19.68 + 20.56}{10} = 20.099 \text{ liters} \][/tex]

3. Find the variance: The variance is a measure of how much the values in the sample differ from the mean. For a sample, the variance ([tex]\(s^2\)[/tex]) is calculated by summing the squared differences from the mean and then dividing by the number of observations minus 1.
[tex]\[ \text{Variance} = \frac{1}{n-1}\sum_{i=1}^{n}(x_i - \bar{x})^2 \][/tex]
Where [tex]\(n = 10\)[/tex] and [tex]\(\bar{x} = 20.099\)[/tex].

Substituting the given data, we get:
[tex]\[ \text{Variance} = 0.14727666666666672 \text{ liters}^2 \][/tex]

4. Calculate the standard deviation: The standard deviation ([tex]\(\sigma\)[/tex]) is the square root of the variance, which provides a measure of the dispersion of the sample data around the mean.
[tex]\[ \text{Standard Deviation} = \sqrt{\text{Variance}} = \sqrt{0.14727666666666672} = 0.3837664220156145 \text{ liters} \][/tex]

Thus, the standard deviation of the sampled containers' contents is approximately [tex]\(0.384\)[/tex], which doesn't exactly match any of the provided options. However, it is closest to:
[tex]\[ \sigma \approx 0.36 \][/tex]

Therefore, the correct answer is:
[tex]\[ \boxed{\sigma = 0.36} \][/tex]