The lengths of a certain species of fish are approximately normally distributed with a given mean [tex][tex]$\mu$[/tex][/tex] and standard deviation [tex][tex]$\sigma$[/tex][/tex]. According to the Empirical Rule, what percentage of the fish will have lengths within 1 standard deviation of the mean?

A. [tex]$34 \%$[/tex]
B. [tex]$47.5 \%$[/tex]
C. [tex]$68 \%$[/tex]
D. [tex]$99.7 \%$[/tex]



Answer :

To determine the percentage of the fish lengths that fall within one standard deviation of the mean using the Empirical Rule, follow these steps:

1. Understand the Empirical Rule:
The Empirical Rule, also known as the 68-95-99.7 rule, is used for normal distributions (bell-shaped curves) and states:
- Approximately 68% of the data falls within one standard deviation ([tex]\(\mu \pm \sigma\)[/tex]) of the mean.
- Approximately 95% of the data falls within two standard deviations ([tex]\(\mu \pm 2\sigma\)[/tex]) of the mean.
- Approximately 99.7% of the data falls within three standard deviations ([tex]\(\mu \pm 3\sigma\)[/tex]) of the mean.

2. Apply the Empirical Rule for 1 standard deviation:
According to the Empirical Rule, around 68% of the data in a normal distribution falls within one standard deviation (i.e., [tex]\(\mu - \sigma\)[/tex] to [tex]\(\mu + \sigma\)[/tex]) of the mean.

3. Identify the Correct Answer:
Based on the Empirical Rule,
- The percentage of data within one standard deviation of the mean is 68%.

Therefore, the correct answer is:
[tex]\[ \boxed{68 \%} \][/tex]