The number of cars sold at a dealership over several weeks is given below:
[tex]\[ 14, 23, 31, 29, 33 \][/tex]

What is the standard deviation for this set of population data?

Standard deviation: [tex]\[\sigma=\sqrt{\frac{\left(x_1-\mu\right)^2+\left(x_2-\mu\right)^2+\ldots+\left(x_N-\mu\right)^2}{N}}\][/tex]

A. 6.9
B. 12.4
C. 15.4
D. 47.2



Answer :

To find the standard deviation of the given dataset [tex]\([14, 23, 31, 29, 33]\)[/tex], we will follow several steps. Let's go through the process step by step.

### Step 1: Calculate the Mean (μ)
The first step is to calculate the mean (average) of the dataset.

[tex]\[ \mu = \frac{\sum_{i=1}^{N} x_i}{N} \][/tex]

where [tex]\( N \)[/tex] is the number of elements in the dataset, and [tex]\( x_i \)[/tex] represents each individual data point.

The dataset consists of 5 values, so [tex]\( N = 5 \)[/tex].

[tex]\[ \mu = \frac{14 + 23 + 31 + 29 + 33}{5} = \frac{130}{5} = 26 \][/tex]

### Step 2: Calculate the Variance for Each Data Point
Next, we calculate the variance for each data point, using the formula:

[tex]\[ (x_i - \mu)^2 \][/tex]

Let’s compute this for each data point:

For [tex]\( x_1 = 14 \)[/tex]:

[tex]\[ (14 - 26)^2 = (-12)^2 = 144 \][/tex]

For [tex]\( x_2 = 23 \)[/tex]:

[tex]\[ (23 - 26)^2 = (-3)^2 = 9 \][/tex]

For [tex]\( x_3 = 31 \)[/tex]:

[tex]\[ (31 - 26)^2 = 5^2 = 25 \][/tex]

For [tex]\( x_4 = 29 \)[/tex]:

[tex]\[ (29 - 26)^2 = 3^2 = 9 \][/tex]

For [tex]\( x_5 = 33 \)[/tex]:

[tex]\[ (33 - 26)^2 = 7^2 = 49 \][/tex]

So, the variances for each data point are [tex]\([144, 9, 25, 9, 49]\)[/tex].

### Step 3: Calculate the Mean of These Variances
To find the standard deviation, we need to calculate the mean of the variances:

[tex]\[ \text{Mean of variances} = \frac{144 + 9 + 25 + 9 + 49}{5} = \frac{236}{5} = 47.2 \][/tex]

### Step 4: Calculate the Standard Deviation (σ)
Finally, the standard deviation (σ) is the square root of the mean of the variances:

[tex]\[ \sigma = \sqrt{47.2} \approx 6.870225614927067 \][/tex]

Therefore, the standard deviation for this set of population data is closest to:

[tex]\[ \boxed{6.9} \][/tex]