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 -2.443°C and -0.119°C.

Solution

To find the probability of obtaining a thermometer reading between 2.443C-2.443^\circ C and 0.119C-0.119^\circ C, given that the readings are normally distributed with a mean μ=0C\mu = 0^\circ C and a standard deviation σ=1C\sigma = 1^\circ C, we can use the standard normal distribution (z-distribution).

Steps:

  1. Convert the values to z-scores: The z-score for a value xx in a normal distribution is calculated using the formula: z=xμσz = \frac{x - \mu}{\sigma}

    • For x1=2.443Cx_1 = -2.443^\circ C: z1=2.44301=2.443z_1 = \frac{-2.443 - 0}{1} = -2.443
    • For x2=0.119Cx_2 = -0.119^\circ C: z2=0.11901=0.119z_2 = \frac{-0.119 - 0}{1} = -0.119
  2. Find the cumulative probabilities for each z-score: Use standard normal distribution tables or a calculator to find the cumulative probabilities for each z-score:

    • P(z1=2.443)P(z_1 = -2.443)
    • P(z2=0.119)P(z_2 = -0.119)
  3. Subtract the cumulative probabilities: The probability of obtaining a reading between 2.443C-2.443^\circ C and 0.119C-0.119^\circ C is: P(2.443<z<0.119)=P(z2)P(z1)P(-2.443 < z < -0.119) = P(z_2) - P(z_1)

Let's compute the exact values.

I will calculate the cumulative probabilities for both z-scores.The probability of obtaining a thermometer reading between 2.443C-2.443^\circ C and 0.119C-0.119^\circ C is approximately 0.4450.445, or 44.5%.

Would you like a more detailed explanation or have any further questions?

Here are 5 related questions you might explore:

  1. What is the probability of a reading being below 0.119C-0.119^\circ C?
  2. How do you find probabilities outside of a given range, such as above 1C1^\circ C?
  3. How does the standard deviation affect the shape of the normal distribution?
  4. What is the probability of obtaining a reading above 1C1^\circ C?
  5. How can z-scores be used to compare different datasets?

Tip: When working with normal distributions, always convert raw scores into z-scores to standardize them for easy probability lookup.

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Math Problem Analysis

Mathematical Concepts

Statistics
Probability
Normal Distribution
Z-scores

Formulas

z = (x - μ) / σ
P(z1 < Z < z2) = P(Z < z2) - P(Z < z1)

Theorems

Empirical Rule
Standard Normal Distribution Theorem

Suitable Grade Level

Grades 10-12