to get a mailbox online go to po boxes online reserve a mailbox by selecting a location and a mailbox size bring two form of ids and form 1583 with you to the post office where your postal box is located get the keys for your boxring two forms of ids with you go to the post office where you want your postal box located save yourself a trip and go online first to check if the size of the postal box you want is available get a po box rental form essentially a variation of form 1583 at the counter
In statistical theory, a U-statistic is a class of statistics that is especially important in estimation theory; the letter U stands for unbiased. In elementary statistics, U-statistics arise naturally in producing minimum-variance unbiased estimators.
Exactly as Gevorg says, we calculate statistics from the sample to make inferences about the parameters of the distribution. With respect to the idea of a sufficient statistic, informally a sufficient statistic is a complete summary of the information in a sample about some parameter of the distribution. From your example, if we assume that the variance of the Gaussian is known, then the sample mean is a sufficient statistic. If you know the sample mean, you have all the information in the sample about the population mean. If you don't know the variance, then the sample mean and the sample variance are sufficient.