Class Notes (835,600)
Sociology (1,100)
SOCY 210 (136)
Lecture 6

# Sampling (week 6).docx

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School
Department
Sociology
Course
SOCY 210
Professor
Vincent F Sacco
Semester
Fall

Description
Sampling  Process of selecting observants  Easier to focus resources on a smaller group o Better than limiting resources on the entire population  People don’t interest us o Interested on attitudes and infer from the greater population  Probability Sampling  Generalizing from a sample to larger population  Uses random selection  Sampling = Political Polling  Sampling Frame o Which population was being sampled  Eg. Telephone subscribers  Automobile owners o List of sampling units  Quota Sampling o Based on knowledge of the characteristics of the population being sampled  Eg. Certain proportions are women, different proportions of incomes, ages o Selects people to match a certain set of characteristics o Quote is based on the variables relevant to the study Types of Sampling Methods  Non Probability Sampling o Reliance on available subjects o Purposive or judgmental sampling o Snow ball sampling o Quota sampling o Qualitative Elements of a population do not stand equal chance of selection o Limit generalizations  Reliance on Available Subjects (Haphazard  Stopping people on a street corner  Doesn’t allow for representativeness of a sample  Cannot over generalize  No criteria for selection of subjects  Useful for pretesting  Purposive Sampling  You select the units to be observed  Personal judgment on who is most useful and representative  General comparisons, cannot overgeneralize  Snowball Sampling  Appropriate when members of a certain population are difficult to locate  Everyone shares the same characteristics  Collect data on a few members of a target population that they can locate  Then ask those individuals to recommend other members of that population  Used for exploratory  Quota Sampling  Units are selected on the basis of prespecified characteristics  Not a random selection  Total sample will have same distribution of characteristics assumed to exist in the population  Bias can occur in choosing those in the sample  Can avoid certain people because they might cause trouble in the study based on appearance Selecting Informants  Respondents o People who provide information about themselves  Informants o Member of a group who can talk directly about the group o Should be representative of the group you want to study  Eg. Cant only study physicians if you want to know about the medical field o Can bias the view you get o Nonprobability sampling  Overall goal o Collect richest possible data o Wide and diverse range of information collected o Relatively a long period of time  Qualitative research studies Probability Sampling  Provide useful descriptions of the total population  Sample of individuals from the population should contain same variations that exist in the actual population o Large scale surveys o Simple random sampling o Systematic sampling  Quantitative  Probability theory o Estimate the accuracy of representiveness in a sample  Representative of larger population  Every unit has known probability of being selected  Can estimate probability o With confidence can make inferences on based on sample for the greater population   Sampling Bias o Those being selected are not representative of the larger population that they are chosen from  Unconsciously avoiding certain people  Representativeness o A sample is representative of the population if the characteristics if the sample are approximate to the same characteristics in the population  Representativeness is limited to those specific characteristics o Randomness  Equal chance of selection  Probability sampling o Representativeness  Generalizability  Inferential statistics o Becomes representative if people from the population being selected have an equal chance of being selected in the sample  EPSEM (equal probability of selection method) o Random selection method  Elements  Certain type of people  Families, clubs  What has equal chance of being selected  Population  Group of elements in a study  What a sample is derived from  All the units that could end up in your sample  Study population 
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