Lecture_3

Example from last class

To select representative sample when there is groups of people:

• Separate sample to different group (eg.SRS of size 80 from group from 800 Group A, then 15 from group from 150 Group B..)

• Combine all 3 groups to get 100 clients <- stratified sampling.

In R

y1 = sample (seq(1,800),size=80)
y2 = sample (seq(801,950),size=15)
y3 = sample (seq(951,1000),size=5)
# in R, you may use c() to represent array.
y = c(y1,y2,y3)

statistical population

v_i_ = response from the i^th client in the population v_i_ = {1:yes,0,no} statistical population = {v_1_,v_2_,…v_1000_}