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 20.84, 19.62, 19.74, 19.72, 20.58, 20.85, 20.99, 19.62, 20.38, and 20.06 liters. Find the standard deviation of the sampled containers' contents.

A. [tex]\sigma=0.38[/tex]
B. [tex]\sigma=0.52[/tex]
C. [tex]\sigma=0.42[/tex]
D. [tex]\sigma=0.53[/tex]



Answer :

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

1. Gather the data:
The contents of the 10 containers are:
[tex]\[ 20.84, 19.62, 19.74, 19.72, 20.58, 20.85, 20.99, 19.62, 20.38, 20.06 \][/tex]

2. Calculate the mean (average) of the data:
First, sum up all the values, then divide by the number of observations.
[tex]\[ \text{Mean} = \frac{20.84 + 19.62 + 19.74 + 19.72 + 20.58 + 20.85 + 20.99 + 19.62 + 20.38 + 20.06}{10} \][/tex]

3. Calculate each value's deviation from the mean:
Subtract the mean from each individual data point to get the deviations.

4. Square each deviation:
This step ensures that all deviations are positive and emphasizes larger deviations.

5. Calculate the variance:
Sum all the squared deviations and divide by the number of observations minus one (N-1, because this is sample variance).
[tex]\[ \text{Variance} = \frac{\sum (\text{deviation}^2)}{10-1} \][/tex]

6. Calculate the standard deviation:
The standard deviation is the square root of the variance.

Given steps, calculations for the mean, deviations, variance, and finally standard deviation yield:
[tex]\[ \sigma \approx 0.552 \][/tex]

So, the correct option that closely matches our calculated standard deviation value is:
D. [tex]\(\sigma=0.53\)[/tex]