25-02-2013, 11:18 AM
Determining the Sample Plan
Determining the Sample.ppt (Size: 770.5 KB / Downloads: 19)
Basic Concepts in Samples and Sampling
Population: the entire group under study as defined by research objectives. Sometimes called the “universe.”
Researchers define populations in specific terms such as heads of households, investors, families, types of retail outlets, etc.
Calculating sample frame error (SFE):
Subtract the number of items on the sampling list from the total number of items in the population.
Take this number and divide it by the total population.
Multiply this decimal by 100 to convert to percent (SFE must be expressed in %)
If the SFE was 40% this would mean that 40% of the population was not in the sampling frame
Reasons for Taking a Sample
Practical considerations such as cost and population size
Inability of researcher to analyze large quantities of data potentially generated by a census
Samples can produce sound results if proper rules are followed for the draw
Basic Sampling Classifications
Probability samples: ones in which members of the population have a known chance (probability) of being selected
Non-probability samples: instances in which the chances (probability) of selecting members from the population are unknown
Online Sampling Techniques
Random online intercept sampling: relies on a random selection of Web site visitors
Invitation online sampling: is when potential respondents are alerted that they may fill out a questionnaire that is hosted at a specific Web site