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Answer:
The minimum sample size required is 71.
Step-by-step explanation:
The (1 - <em>α</em>)% confidence interval for population mean is:
The margin of error for this interval is:
It is provided that the population standard deviation <em>σ</em> can be estimated by the sample standard deviation <em>s</em>.
The given information is:
<em>s</em> = 18000,
Margin of error = $4200.
Confidence level = 95%
The <em>z</em>-value for 95% confidence level is,
*Use a <em>z</em>-table for the critical value.
Compute the sample size required as follows:
Thus, the minimum sample size required is 71.