Math Problem Statement
Given two dependent random samples with the following results:
Population 1
30
15
28
44
26
47
32
Population 2
44
28
36
35
18
35
22
Use this data to find the 95% confidence interval for the true difference between the population means. Assume that both populations are normally distributed.
Step 3 of 4 :
Calculate the margin of error to be used in constructing the confidence interval. Round your answer to six decimal places.
Solution
To calculate the margin of error (ME) for the 95% confidence interval for the difference between the means of two dependent random samples, we proceed with the following steps:
Step 1: Compute the differences () between the paired values
Let .
[ d = [30-44, 15-28, 28-36, 44-35, 26-18, 47-35, 32-22] = [-14, -13, -8, 9, 8, 12, 10] ]
Step 2: Calculate the mean of the differences ()
Step 3: Calculate the standard deviation of the differences ()
The formula for is:
First, calculate each :
Sum these values:
Now calculate :
Step 4: Calculate the standard error of the mean difference ()
The formula for is:
Step 5: Find the critical value for a 95% confidence level ()
For degrees of freedom and a 95% confidence level, the critical -value is approximately (from a -distribution table).
Step 6: Calculate the margin of error (ME)
The formula for is:
Final Answer:
The margin of error is:
Let me know if you'd like further clarification or assistance with this problem. Here are five related questions to expand on this topic:
- How is the -value chosen for constructing the confidence interval?
- Why is the paired sample standard deviation used instead of individual standard deviations?
- What changes in the calculation if the samples were independent instead of paired?
- How does increasing the sample size affect the margin of error?
- Can the confidence interval be interpreted as a probability statement?
Tip: Always verify whether the assumptions (normality and paired data) are satisfied before using -distribution methods for confidence intervals.
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Math Problem Analysis
Mathematical Concepts
Confidence Interval
Paired Sample t-Test
Normal Distribution
Statistics
Formulas
Mean difference: \(\bar{d} = \frac{\sum d_i}{n}\)
Standard deviation of differences: \(s_d = \sqrt{\frac{\sum (d_i - \bar{d})^2}{n-1}}\)
Standard error: \(SE_d = \frac{s_d}{\sqrt{n}}\)
Margin of error: \(ME = t^* \cdot SE_d\)
Theorems
Central Limit Theorem
t-Distribution
Suitable Grade Level
Undergraduate - Introductory Statistics
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