Math Problem Statement

Assume that a randomly selected subject is given a score density test. These test scores are normally distributed with a mean of 0 and a standard deviation of 1. Find the probability that a given score is less than 1.05 and draw a sketch of the region. Select the region. Choose the correct graph below.

Solution

The problem asks to find the probability that a given score is less than 1.05 using a normal distribution. Here's a breakdown of the situation based on the image:

  1. The scores are normally distributed with a mean of 0 and a standard deviation of 1.
  2. The task is to determine which graph correctly represents the cumulative area under the curve to the left of x=1.05x = 1.05, which corresponds to finding P(X<1.05)P(X < 1.05).

Standard Normal Distribution

For a standard normal distribution (mean = 0, standard deviation = 1), we need to find the cumulative probability for z=1.05z = 1.05.

Using the Z-score table, P(Z<1.05)0.8531P(Z < 1.05) \approx 0.8531.

This means that about 85.31% of the data lies below a Z-score of 1.05, so the correct graph should show an area under the curve to the left of x=1.05x = 1.05 that covers about 85% of the total area.

Graph Interpretation

Based on the question:

  • The correct graph should shade a large portion of the left side of the curve (about 85%).
  • The peak should be centered at x=0x = 0, with a standard bell curve extending on both sides.

Graph C appears to match this description since it shows most of the area under the curve shaded to the left of x=1.05x = 1.05, which is consistent with the solution from the Z-score table.

Answer:

The correct option is C.


Would you like further details on how this problem is solved or explanations of related concepts?

Here are five related questions you might find useful:

  1. How do you use a Z-score table to find probabilities?
  2. What is the standard normal distribution, and why is it important?
  3. How do you calculate the Z-score for a data point from any normal distribution?
  4. How do cumulative probabilities work in a normal distribution?
  5. What is the significance of the area under the curve in probability?

Tip: When working with normal distributions, the Z-score allows you to compare values from any normal distribution to the standard normal distribution.

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Math Problem Analysis

Mathematical Concepts

Probability
Normal Distribution
Z-Score

Formulas

Z = (X - μ) / σ
P(X < z)

Theorems

Standard Normal Distribution
Empirical Rule

Suitable Grade Level

Grades 10-12