Math Problem Statement
You may need to use the appropriate appendix table to answer this question. Automobile repair costs continue to rise with the average cost now at $367 per repair.† Assume that the cost for an automobile repair is normally distributed with a standard deviation of $88. Answer the following questions about the cost of automobile repairs. (a) What is the probability that the cost will be more than $460? (Round your answer to four decimal places.) 0.15876
Incorrect: Your answer is incorrect. (b) What is the probability that the cost will be less than $250? (Round your answer to four decimal places.) 0.1587
Incorrect: Your answer is incorrect. (c) What is the probability that the cost will be between $250 and $460? (Round your answer to four decimal places.) 0.6826
Incorrect: Your answer is incorrect. (d) If the cost for your car repair is in the lower 5% of automobile repair charges, what is your maximum possible cost in dollars? (Round your answer to the nearest cent.) $ 224.54
Incorrect: Your answer is incorrect.
Solution
To solve these questions, we'll use the properties of the normal distribution, specifically the Z-score formula and standard normal distribution tables (or a calculator).
Given:
- Mean (μ) = $367
- Standard Deviation (σ) = $88
(a) Probability that the cost will be more than $460
-
Calculate the Z-score:
-
Find the probability from the Z-table: Look up . The cumulative probability for is approximately 0.8554.
-
Calculate the probability of being more than $460:
(b) Probability that the cost will be less than $250
-
Calculate the Z-score:
-
Find the probability from the Z-table: Look up . The cumulative probability for is approximately 0.0918.
(c) Probability that the cost will be between $250 and $460
-
Using previously found probabilities: From earlier:
-
Calculate:
(d) Maximum cost in the lower 5% of automobile repair charges
-
Find the Z-score corresponding to the lower 5%: The Z-score for the lower 5% is approximately -1.645.
-
Calculate the maximum cost:
Summary of Results:
- (a)
- (b)
- (c)
- (d) Maximum cost in the lower 5% is approximately $221.44.
If you would like further details or clarifications, feel free to ask! Here are some related questions you might consider:
- How do you interpret the results of normal distribution probabilities?
- What other factors could influence automobile repair costs?
- How would changes in the mean or standard deviation affect the probabilities?
- What is the significance of the lower 5% in practical terms?
- Can you explain the concept of Z-scores in more detail?
Tip: Always ensure that you round correctly based on the context of the problem, as it can significantly affect your final answers.
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Math Problem Analysis
Mathematical Concepts
Probability
Normal Distribution
Z-scores
Formulas
Z = (X - μ) / σ
P(X > a) = 1 - P(Z < z)
P(a < X < b) = P(X < b) - P(X < a)
Theorems
Properties of the normal distribution
Central Limit Theorem
Suitable Grade Level
Grades 11-12
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