# (c) Give a brief outline describing how the sample size for a predetermined error tolerance and level of confidence is determined from the normal distribution.

(c) Give a brief outline describing how the sample size for a predetermined error tolerance and level of confidence is determined from the normal distribution.
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curwyrm
Firstly, it is assumed that the sample mean is normally distributed.
For determining the sample size, it is necessary to know the value of the sample standard deviation. If the value of the standard deviation is not known, then use some preliminary data for approximating it.
When the sample size is equal to or greater than 30, the sample standard deviation is approximated to the population standard deviation $\left(\sigma \right)$. The sample size for predetermined error tolerance (E) and confidence interval using the normal distribution is given as follows:
$n={\left({z}_{c}×\frac{\sigma }{E}\right)}^{2}$