Math Problem Statement

Suppose Z follows the standard normal distribution. Calculate the following probabilities: (a) P(Z > 0.58) (b) P(Z ≤ 1.90) (c) P(-0.76 < Z < 2.15)

Solution

Let's solve these probabilities for the standard normal distribution ZZ. I'll calculate each part separately:

Given Information:

The variable ZZ follows a standard normal distribution, meaning ZN(0,1)Z \sim N(0,1). We will use the standard normal distribution table (z-table) or calculator to find the probabilities.

Solutions:

(a) P(Z>0.58)P(Z > 0.58)

This is the probability that ZZ is greater than 0.58.

  1. Using the z-table or calculator, find P(Z0.58)P(Z \leq 0.58) and then subtract from 1 to get P(Z>0.58)P(Z > 0.58).
  2. P(Z0.58)0.7190P(Z \leq 0.58) \approx 0.7190.
  3. Therefore, P(Z>0.58)=10.7190=0.2810P(Z > 0.58) = 1 - 0.7190 = 0.2810.

(b) P(Z1.90)P(Z \leq 1.90)

This is the probability that ZZ is less than or equal to 1.90.

  1. Using the z-table or calculator, find P(Z1.90)P(Z \leq 1.90).
  2. P(Z1.90)0.9713P(Z \leq 1.90) \approx 0.9713.

(c) P(0.76<Z<2.15)P(-0.76 < Z < 2.15)

This is the probability that ZZ is between -0.76 and 2.15.

  1. First, find P(Z2.15)P(Z \leq 2.15) and P(Z0.76)P(Z \leq -0.76).
  2. P(Z2.15)0.9842P(Z \leq 2.15) \approx 0.9842 and P(Z0.76)0.2236P(Z \leq -0.76) \approx 0.2236.
  3. P(0.76<Z<2.15)=P(Z2.15)P(Z0.76)=0.98420.2236=0.7606P(-0.76 < Z < 2.15) = P(Z \leq 2.15) - P(Z \leq -0.76) = 0.9842 - 0.2236 = 0.7606.

Answers:

  • (a) P(Z>0.58)=0.281P(Z > 0.58) = 0.281
  • (b) P(Z1.90)=0.971P(Z \leq 1.90) = 0.971
  • (c) P(0.76<Z<2.15)=0.761P(-0.76 < Z < 2.15) = 0.761

Would you like more details on any of these steps, or do you have any questions?

Here are some related questions to explore further:

  1. How would you find P(Z<1.25)P(Z < -1.25)?
  2. What is the probability P(Z1.00)P(Z \geq -1.00)?
  3. How would you calculate P(0<Z<1.5)P(0 < Z < 1.5)?
  4. What does it mean if ZN(0,1)Z \sim N(0,1)?
  5. How would the probabilities change if the distribution was not standard normal?

Tip: When working with standard normal probabilities, it helps to remember that the total area under the curve is 1, so you can often use complements (1 - probability) for calculations.

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Math Problem Analysis

Mathematical Concepts

Probability
Standard Normal Distribution
Z-Scores

Formulas

P(Z > z) = 1 - P(Z ≤ z)
P(a < Z < b) = P(Z ≤ b) - P(Z ≤ a)

Theorems

Standard Normal Distribution Properties
Complement Rule

Suitable Grade Level

Undergraduate