Population And Sampling

Population And Sampling

1. Population

   • the total set of observations that can be made

2. Census

   • When all of the data in the population is taken
     • National census: an official enumeration of the population
   • Disadvantages
     • Time Consuming
     • Exspenisve
     • Difficult to ensure whole population is surveyed
   • Advantages
     • Unbiased
     • Takes account of whole population
     • Accurate

3. Sample

   • When data is collected from part of the population
   • Advantages
     • Cheaper
     • Less time consuming
     • Less data to be analysed
   • Disadvantages
     • Not completely representative
     • Possibly biased

4. Random Sample

   • The sample is picked without bias/not in a sepcific order
   • 1.Define the population
     • 2.Choose your sample size
       • 3. List the population
         • 4.Assign numbers to the units
           • 5. Use random number generator on calculator
             • 6. Select your sample

5. Stratified Sampling

   • Where the data is in proportion to the population
   • 1. number each peice of data
     • 2. use a random number generator
       • 3. Select random numbers
         • 4. The sample should be representative

6. Quota Sampling

   • representative individuals are chosen out of a specific subgroup

7. Conenience Sampling

   • Made up of people who are easy to reach.

8. Cluster Sampling

   • the population is divided into separate groups

9. Systamatic Sampling

   • members from a larger population are selected according to a random starting point and a fixed, periodic interval