Math Problem Statement
The lifetime of a certain type of battery is known to be normally distributed with standard deviation o = 17 hours. A sample of 50 batteries had a mean lifetime of 120.1 hours. It is desired to construct a 95% confidence interval for the mean lifetime for this type of battery. What is the point estimate? Find the standard error
Solution
Solution:
Step 1: Point Estimate
The point estimate for the population mean is the sample mean. In this case:
Step 2: Standard Error of the Mean
The standard error (SE) of the sample mean is calculated using the formula:
where:
- (population standard deviation),
- (sample size).
Substitute the values:
First, calculate :
Now calculate the standard error:
Final Results:
- Point Estimate: hours.
- Standard Error: hours.
Would you like help constructing the full confidence interval or understanding the steps in more detail?
Expanding Questions:
- How is the confidence interval calculated using the point estimate and standard error?
- What is the interpretation of a 95% confidence interval in this context?
- How does increasing the sample size affect the standard error and confidence interval?
- What if the population standard deviation was unknown? How would the method change?
- How can hypothesis testing be applied to determine if the true mean differs from a specific value?
Tip:
The standard error decreases as the sample size increases, leading to a narrower confidence interval and greater precision.
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Math Problem Analysis
Mathematical Concepts
Statistics
Confidence Intervals
Standard Error
Formulas
Point Estimate: \( \bar{x} = \text{sample mean} \)
Standard Error: \( SE = \frac{\sigma}{\sqrt{n}} \)
Theorems
Central Limit Theorem (for sample means)
Suitable Grade Level
Grades 11-12 or introductory college level
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