A supervisor finds the mean number of miles that the employees in a department live from work. He finds [tex]\bar{x} = 29[/tex] and [tex]s = 3.6[/tex]. Which statement must be true?

A. [tex]2y y[/tex] is within 1 standard deviation of the mean.
B. [tex]z_{37}[/tex] is between 1 and 2 standard deviations of the mean.
C. [tex]z_{37}[/tex] is between 2 and 3 standard deviations of the mean.
D. [tex]z_{37}[/tex] is more than 3 standard deviations of the mean.



Answer :

To determine which statement is true about the distance of 37 miles from the mean, we will follow these steps:

1. Calculate the Z-score for 37 miles:
The Z-score tells us how many standard deviations a data point is from the mean. The formula for the Z-score is:
[tex]\[ z = \frac{y - \bar{x}}{s} \][/tex]
Where:
- [tex]\( y \)[/tex] is the value we're interested in (37 miles).
- [tex]\( \bar{x} \)[/tex] is the mean (29 miles).
- [tex]\( s \)[/tex] is the standard deviation (3.6 miles).

2. Substitute the values into the formula:
[tex]\[ z_{37} = \frac{37 - 29}{3.6} \][/tex]

3. Perform the subtraction and division:
[tex]\[ z_{37} = \frac{8}{3.6} = 2.2222222222222223 \][/tex]

So, the Z-score for 37 miles is approximately [tex]\( 2.222 \)[/tex].

4. Determine which interval the Z-score falls into:
- If the Z-score is less than or equal to 1, the value is within 1 standard deviation of the mean.
- If the Z-score is between 1 and 2, the value is between 1 and 2 standard deviations of the mean.
- If the Z-score is between 2 and 3, the value is between 2 and 3 standard deviations of the mean.
- If the Z-score is greater than 3, the value is more than 3 standard deviations from the mean.

Since [tex]\( z_{37} = 2.222 \)[/tex]:

- It is not within 1 standard deviation of the mean.
- It is not between 1 and 2 standard deviations of the mean.
- It is between 2 and 3 standard deviations of the mean.
- It is not more than 3 standard deviations from the mean.

Therefore, the correct statement is:
[tex]\[ z_{37} \text{ is between 2 and 3 standard deviations of the mean.} \][/tex]