How do you calculate the parameter to a 99.9 confidence interval using mean and standard deviation?

How do you calculate the parameter to a 99.9 confidence interval using mean and standard deviation?
Did you mean, "How do you calculate the 99.9 % confidence interval to a parameter using the mean and the standard deviation?" ?
The parameter is the population mean . Let xbar and s denote the sample mean and the sample standard deviation. The formula for a 99.9% confidence limit for is
xbar - 3.08 s / n and
xbar + 3.08 s / n
where xbar is the sample mean, n the sample size and s the sample standard deviation. 3.08 comes from a Normal probability table.