Answer :
The answers are: a) t-distribution will be used b) the confidence interval is 32.260 < Population Mean < 34.940 c) sampling process and assumptions are valid.
a. To compute the confidence interval, we will use the t-distribution since the sample size is relatively small (147 residents).
b. The formula for the confidence interval for the population mean is given by:
Confidence Interval = Sample Mean ± Margin of Error
Where the margin of error is:
Margin of Error = Critical Value × Standard Error
Standard Error = Standard Deviation / √Sample Size
For a 95% confidence level, the critical value for a t-distribution with 146 degrees of freedom (147 - 1) is approximately 1.9785 (you can look this up in a t-table or calculator).
Given:
Sample Mean = 33.6 pounds
Standard Deviation (σ) = 8.2 pounds
Sample Size (n) = 147
Critical Value = 1.9785 (for a 95% confidence level)
Calculate the Standard Error:
Standard Error = 8.2 / √147 ≈ 0.6772
Calculate the Margin of Error:
Margin of Error = 1.9785 × 0.6772 ≈ 1.3399
So, the confidence interval is:
33.6 - 1.3399 < Population Mean < 33.6 + 1.3399
32.2601 < Population Mean < 34.9399
Rounded to three decimal places, the interval is:
32.260 < Population Mean < 34.940
c. About 95% of these confidence intervals will contain the true population mean number of pounds of trash generated per person per week, while about 5% will not contain the true population mean. This is because of the nature of confidence intervals, which are constructed to provide a certain level of confidence (in this case, 95%) that the true population parameter lies within the interval. This assumes that the sampling process and assumptions are valid.
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