Pregunta
sume the random variable \( x \) is normally distributed with mean \( \mu=50 \) and standard deviation \( \sigma=7 \). Find the indicate obability. \( P(x>37) \) \( (x>37)=\square \) ound to four decimal places as needed.)
Ask by Barber Lowe. in the United States
Feb 03,2025
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The probability that \( x > 37 \) is 0.9684.
Solución
To find the probability \( P(x > 37) \) for a normally distributed random variable \( x \) with mean \( \mu = 50 \) and standard deviation \( \sigma = 7 \), follow these steps:
1. **Standardize the Variable:**
Convert the original variable \( x \) to a standard normal variable \( z \) using the formula:
\[
z = \frac{x - \mu}{\sigma}
\]
For \( x = 37 \):
\[
z = \frac{37 - 50}{7} = \frac{-13}{7} \approx -1.8571
\]
2. **Find the Probability:**
We need to find \( P(x > 37) \), which is equivalent to \( P(z > -1.8571) \).
Due to the symmetry of the normal distribution:
\[
P(z > -1.8571) = 1 - P(z < -1.8571) = P(z < 1.8571)
\]
Using standard normal distribution tables or a calculator, find \( \Phi(1.8571) \), where \( \Phi \) denotes the cumulative distribution function (CDF) of the standard normal distribution.
3. **Lookup or Calculate \( \Phi(1.8571) \):**
- For \( z = 1.85 \), \( \Phi(1.85) \approx 0.9678 \)
- For \( z = 1.86 \), \( \Phi(1.86) \approx 0.9686 \)
Interpolating for \( z = 1.8571 \):
\[
\Phi(1.8571) \approx 0.9678 + \frac{0.0008}{0.01} \times 0.0071 \approx 0.9684
\]
4. **Conclusion:**
\[
P(x > 37) = 0.9684
\]
**Final Answer:**
\[
P(x > 37) = 0.9684
\]
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Mind Expander
To find \( P(x > 37) \), we first convert the value to a z-score using the formula: \[ z = \frac{x - \mu}{\sigma} = \frac{37 - 50}{7} \approx -1.8571 \] Next, we look up this z-score in the standard normal distribution table or use a calculator to find \( P(Z < -1.8571) \). This gives us approximately \( 0.0316 \). Therefore, to find \( P(x > 37) \): \[ P(x > 37) = 1 - P(Z < -1.8571) \approx 1 - 0.0316 = 0.9684 \] Thus, \( P(x > 37) \approx 0.9684 \).
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