Math Problem Statement

Let Z ~ N(0,1). Find a so that P(Z > a) = 0.24.

Solution

The question asks to find aa such that P(Z>a)=0.24P(Z > a) = 0.24, where ZN(0,1)Z \sim N(0, 1) is a standard normal distribution.

This is essentially asking for the value of aa such that the probability that ZZ (a standard normal random variable) is greater than aa is 0.24. In terms of the cumulative distribution function (CDF) Φ(a)\Phi(a), this can be written as:

P(Z>a)=1Φ(a)=0.24P(Z > a) = 1 - \Phi(a) = 0.24

Therefore, Φ(a)=10.24=0.76\Phi(a) = 1 - 0.24 = 0.76. Now, we need to find the value of aa such that Φ(a)=0.76\Phi(a) = 0.76, which corresponds to finding the inverse of the standard normal distribution for a probability of 0.76.

Let me calculate that for you.The value of aa such that P(Z>a)=0.24P(Z > a) = 0.24 is approximately a=0.71a = 0.71.

Would you like a detailed explanation of the steps, or do you have any questions?

Here are 5 related questions to expand your understanding:

  1. What is the significance of the cumulative distribution function (CDF) in statistics?
  2. How do you calculate probabilities for non-standard normal distributions?
  3. What is the relationship between percentiles and standard scores (z-scores)?
  4. How would the calculation change if the probability given was P(Z<a)P(Z < a)?
  5. How does the area under the standard normal curve help in understanding probabilities?

Tip: When working with standard normal distributions, remember that the total area under the curve is 1, and the curve is symmetric about the mean, Z=0Z = 0.

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Math Problem Analysis

Mathematical Concepts

Probability
Standard Normal Distribution
Cumulative Distribution Function (CDF)

Formulas

P(Z > a) = 1 - Φ(a)
Φ(a) = CDF of the standard normal distribution
Inverse CDF to find a

Theorems

Standard Normal Distribution Theorem
Cumulative Distribution Theorem

Suitable Grade Level

College Level (Undergraduate Statistics)