The sample size of the population to 99% confidence interval for the population mean is 166.
The formula to the sample size is n = (zⁿ ×∝÷ E)
where = Z critical z value ( confidence level) ,
E = Margin of error,
= population standard deviation.
Here E= 1.3
Critical z-value for 99% confidence level = 2.576
A random variable, sample, statistical population, data set, or probability distribution's standard deviation is equal to the square root of its variance. Although less robust in practice, it is algebraically easier than the average absolute deviation.
Then, required sample size :
n= (6.9 × 2.576÷2.3)² = 7.728²
59.72≈ 60
n = (6.0 × 2.765÷ 1.2)²
= 12.88²
169.89 ≈ 166
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