SIMPLE RANDOM 

 SAMPLING 





STRATIFIED RANDOM 

 SAMPLING 



• STRATA 



PRIMARY- 

 UNITS 



TWO-STAGE 

 SAMPLING 



CLUSTER 

 SAMPLING 



• - •/ 



(^ 



• CLUSTERS 



SYSTEMATIC GRID 

 SAMPLING 



• • • • 



• • • • 



• • • • 



RANDOM SAMPLING 

 WITHIN BLOCKS 



• •_ 



Reference: Gilbert (1987) 



Figure 5 General sampling station layouts for probability sampling in 

 two dimensions. 



