SIMPLE RANDOM SAMPLING

1
SIMPLE RANDOM SAMPLING
Simple - Sample was selected from an undivided
population. Random - Each unit in the population
has the same probability of being
selected. Different than aimlessness
2
Stratification Sampling

• PSYCHOLOGY MAJORS
• A separate sample is randomly selected from each
  stratum (or layer) of the population.

Female 80
Male 20
3
Area Probability Sampling

• CMU Residence Hall Students
• Divide population based on meaningful geographic
  areas.

Northwest Quad 1000 students
South Quad 900 Students
South West Quad 2500 Students
South East Quad 800 students
4
Bias due to Nonresponse

• 3,116 Total Population(NC peach growers)

Nonrespondents 1,839 59
300 10
543 17
434 14
5
Bias due to Nonresponse

• Mean Trees for each group (M329)

Nonrespondents 290
456
382
340
6
Increasing Rate of Response

• Mail Surveys
• Mail more than one questionnaire
• Call nonrespondents
• Incentives
• Use special delivery or hand stamped
• Make questionnaires clear, easy to read, and
  attractive layout

7
Increasing Rate of Response

• Phone Survey
• Send advanced letter
• Pilot testing
• Call on weekend and/or evenings