Chapter 14. Sampling. Learning Objectives. Understand . . . The two premises on which sampling theory is based. The accuracy and precision for measuring sample validity. The five questions that must be answered to develop a sampling plan. Learning Objectives. Understand . . .
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Understand . . .
Understand . . .
“We have to hear what’s being said in a natural environment, and social media is an obvious place to do this, but we also have to go and discover the opinions that are not being openly shared. Only then can we understand the dichotomy between the public and private persona.”
Ben Leet, sales director
SampleThe Nature of Sampling
Availability of elements
“In recent Gallup ‘Poll on polls,’ . . . When asked about the scientific sampling foundation on which polls are based . . . most said that a survey of 1,500 – 2,000 respondents—a larger than average sample size for national polls—cannot represent the views of all Americans.”
The Gallup Poll editor in chief
The Gallup Organization
What is the target population?
What are the parameters of interest?
What is the sampling frame?
What is the appropriate sampling method?
What size sample is needed?
Number of subgroups
Small error rangeWhen to Use Larger Sample?
with random dialing
List of elements in population
Complete and correct
Error rate increases over time
May include elements that
must be screened out
Well defined political or
No need to generalize
Additional Discussion opportunities
Dealers control 75% of advertising
Recruited 30 influential dealers
Morpace conducted focus groups
72-hour marathon of questions
Gave voice to important group
“The proof of the pudding is in the eating. By a small sample we may judge of the whole piece.”
Miguel de Cervantes Saavedra
The average number of text messages sent per day by