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The heights of the trees in a forest are normally distributed, with a mean of 25 meters and a standard deviation of 6 meters. What is the probability that a randomly selected tree in the forest has a height greater than or equal to 37 meters? Use the portion of the standard normal table given to help answer the question.

\begin{tabular}{|c|c|}
\hline
[tex]$z$[/tex] & Probability \\
\hline
0.00 & 0.5000 \\
\hline
0.50 & 0.6915 \\
\hline
1.00 & 0.8413 \\
\hline
2.00 & 0.9772 \\
\hline
3.00 & 0.9987 \\
\hline
\end{tabular}

A. [tex]$0.13 \%$[/tex]
B. [tex]$0.26 \%$[/tex]
C. [tex]$2.3 \%$[/tex]
D. [tex]$4.6 \%$[/tex]


Sagot :

To determine the probability that a randomly selected tree in the forest has a height greater than or equal to 37 meters, follow these steps:

1. Identify the parameters of the normal distribution:
- Mean ([tex]\(\mu\)[/tex]) = 25 meters.
- Standard deviation ([tex]\(\sigma\)[/tex]) = 6 meters.

2. Find the z-score for the height threshold (37 meters):
The z-score is a measure of how many standard deviations an element is from the mean. It is calculated using the formula:
[tex]\[ z = \frac{X - \mu}{\sigma} \][/tex]
where [tex]\(X = 37\)[/tex] meters.
[tex]\[ z = \frac{37 - 25}{6} = \frac{12}{6} = 2.0 \][/tex]

3. Locate the cumulative probability for the z-score of 2.0 in the standard normal distribution table:
According to the given table:
[tex]\[ \begin{array}{|c|c|} \hline z & \text{Probability} \\ \hline 2.00 & 0.9772 \\ \hline \end{array} \][/tex]
This probability (0.9772) represents the area to the left of [tex]\(z = 2.0\)[/tex].

4. Determine the probability of a tree having a height greater than or equal to 37 meters:
Since we need the probability of a height greater than or equal to 37 meters, we are interested in the right tail of the distribution. The area to the right of [tex]\(z = 2.0\)[/tex] can be found by subtracting the cumulative probability from 1.
[tex]\[ P(X \geq 37) = 1 - P(X < 37) = 1 - 0.9772 = 0.0228 \][/tex]

5. Convert the probability into percentage:
[tex]\[ P(X \geq 37) \times 100 = 0.0228 \times 100 = 2.28\% \][/tex]

So, the probability that a randomly selected tree in the forest has a height greater than or equal to 37 meters is approximately [tex]\(2.3\% \)[/tex].