burnsy562000

Sampling and Estimation:
t-stat: (point of estimation of the population mean) +/- (reliability factor t-stat) X (standard of error)
* This is used for confidence interval for two-tailed distribution

while

Hypothesis Testing:
z-stat: (sample mean - hypothsized mean)/ (standard of error)
The above is the general formulae. If variance is known, it will be z-distribution. And if variance unknown, its for t-distribution.