Assume 2 is a random variable with a standard normal distribution and a is a positive number. If P(Z > a) = 0.1, then P(-a < Z

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**Question Explanation and Concept:**

Assume \( Z \) is a random variable with a standard normal distribution and \( a \) is a positive number. If \(\mathbb{P}(Z > a) = 0.1\), then \(\mathbb{P}(-a < Z < a) = 0.8.\)

**Question Statement:**

True or False
- ( ) True
- ( ) False

**Explanation:**

Here, \( Z \) represents a standard normal random variable, which implies it follows a normal distribution with a mean of 0 and a standard deviation of 1.

Let’s analyze the given conditions:

1. \(\mathbb{P}(Z > a) = 0.1\)

This condition means the probability that \( Z \) is greater than \( a \) is 0.1. Because the standard normal distribution is symmetric about the mean (0), the probability \( \mathbb{P}(Z < -a) \) will also be 0.1.

2. The probability for the range \( -a < Z < a \) can be interpreted as the area under the normal curve within these limits. To find this, observe that:

\[
\mathbb{P}(Z > a) + \mathbb{P}(Z < -a) + \mathbb{P}(-a < Z < a) = 1
\]

Given \(\mathbb{P}(Z > a) = 0.1\) and \( \mathbb{P}(Z < -a) = 0.1 \), the combined probabilities for the tails are:

\[
\mathbb{P}(Z > a) + \mathbb{P}(Z < -a) = 0.1 + 0.1 = 0.2
\]

So, the probability within \( -a \) and \( a \):

\[
\mathbb{P}(-a < Z < a) = 1 - 0.2 = 0.8
\]

Given this calculation, the statement:

"If \(\mathbb{P}(Z > a) = 0.1\), then \(\mathbb{P}(-a < Z < a) = 0.8\)"

is **True**.
Transcribed Image Text:**Question Explanation and Concept:** Assume \( Z \) is a random variable with a standard normal distribution and \( a \) is a positive number. If \(\mathbb{P}(Z > a) = 0.1\), then \(\mathbb{P}(-a < Z < a) = 0.8.\) **Question Statement:** True or False - ( ) True - ( ) False **Explanation:** Here, \( Z \) represents a standard normal random variable, which implies it follows a normal distribution with a mean of 0 and a standard deviation of 1. Let’s analyze the given conditions: 1. \(\mathbb{P}(Z > a) = 0.1\) This condition means the probability that \( Z \) is greater than \( a \) is 0.1. Because the standard normal distribution is symmetric about the mean (0), the probability \( \mathbb{P}(Z < -a) \) will also be 0.1. 2. The probability for the range \( -a < Z < a \) can be interpreted as the area under the normal curve within these limits. To find this, observe that: \[ \mathbb{P}(Z > a) + \mathbb{P}(Z < -a) + \mathbb{P}(-a < Z < a) = 1 \] Given \(\mathbb{P}(Z > a) = 0.1\) and \( \mathbb{P}(Z < -a) = 0.1 \), the combined probabilities for the tails are: \[ \mathbb{P}(Z > a) + \mathbb{P}(Z < -a) = 0.1 + 0.1 = 0.2 \] So, the probability within \( -a \) and \( a \): \[ \mathbb{P}(-a < Z < a) = 1 - 0.2 = 0.8 \] Given this calculation, the statement: "If \(\mathbb{P}(Z > a) = 0.1\), then \(\mathbb{P}(-a < Z < a) = 0.8\)" is **True**.
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