Survey sampling
(ullet)What is survey sampling?(c.f.census survey)(c.f.:参考，查看，来源于拉丁语)
(ullet)understanding the whole by a (underline{fraction})(i.e.a (underline{sample}))
Population:
Q:What is the population to survey?(In some cases,it can be difficult to identify or determine)
N:population size
a sample of size n:a subgroup of n members(n<N)
Q:Which n members should be included in the sample?(i.e.how to produce a (underline{representative}) sample)
quantity of interest:
(x_i,i=1,2,3cdots N)(each labeled by an integer)
(x_i)can be (underline{numerical}) or (underline{categorial})
Multivariate((x_{i1},x_{i2}cdots x_{ik}),i=1,2,3 dots N)
(underline{Definition : })(survey sampling)
A technique to obtain (underline{information}) about a (underline{large}) population by examining only