Math Problem Statement

Assume that the readings at freezing on a batch of thermometers are normally distributed with a mean of 0°C and a standard deviation of 1.00°C. A single thermometer is randomly selected and tested. Find the probability of obtaining a reading between 0°C and 0.94°C.

Solution

To solve this problem, we will use the standard normal distribution (Z-distribution) since the thermometer readings are normally distributed with a mean (μ\mu) of 0C0^\circ\text{C} and a standard deviation (σ\sigma) of 1C1^\circ\text{C}.

Step-by-Step Solution:

  1. Define the Problem:

    • Mean (μ\mu) = 0C0^\circ\text{C}
    • Standard Deviation (σ\sigma) = 1C1^\circ\text{C}
    • Find the probability P(0X0.94)P(0 \leq X \leq 0.94), where XX is the reading.
  2. Convert to Z-scores: The Z-score formula is: Z=XμσZ = \frac{X - \mu}{\sigma} For X=0X = 0: Z1=001=0Z_1 = \frac{0 - 0}{1} = 0 For X=0.94X = 0.94: Z2=0.9401=0.94Z_2 = \frac{0.94 - 0}{1} = 0.94

  3. Find the Corresponding Probabilities: Using a standard normal table or a calculator:

    • For Z=0Z = 0, the cumulative probability is: P(Z0)=0.5P(Z \leq 0) = 0.5
    • For Z=0.94Z = 0.94, the cumulative probability is approximately: P(Z0.94)=0.8264P(Z \leq 0.94) = 0.8264
  4. Calculate the Desired Probability: The probability of obtaining a reading between 0C0^\circ\text{C} and 0.94C0.94^\circ\text{C} is: P(0X0.94)=P(Z0.94)P(Z0)P(0 \leq X \leq 0.94) = P(Z \leq 0.94) - P(Z \leq 0) Substituting the values: P(0X0.94)=0.82640.5=0.3264P(0 \leq X \leq 0.94) = 0.8264 - 0.5 = 0.3264

Final Answer:

The probability of obtaining a reading between 0C0^\circ\text{C} and 0.94C0.94^\circ\text{C} is 0.3264 (or 32.64%).


Would you like further clarification or additional examples?

Here are 5 related questions to expand your understanding:

  1. What is the probability of obtaining a reading less than 0.5C-0.5^\circ\text{C}?
  2. How would the probability change if the standard deviation was 0.5°C instead of 1°C?
  3. What is the probability of obtaining a reading greater than 1.5C1.5^\circ\text{C}?
  4. How can we calculate probabilities for readings in a non-standard normal distribution?
  5. How do cumulative distribution functions (CDFs) help in solving such problems?

Tip: Always check if the distribution is standard normal or requires a Z-score transformation!

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Math Problem Analysis

Mathematical Concepts

Probability
Normal Distribution
Z-scores

Formulas

Z = (X - μ) / σ
P(a ≤ X ≤ b) = P(Z ≤ Zb) - P(Z ≤ Za)

Theorems

Properties of the Standard Normal Distribution

Suitable Grade Level

Grades 9-12