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What are the Odds? Sampling Theory and Logic. Let’s Be Realistic… It’s unlikely you’ll be in a position to do much sampling in your daily work Important.

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Presentation on theme: "What are the Odds? Sampling Theory and Logic. Let’s Be Realistic… It’s unlikely you’ll be in a position to do much sampling in your daily work Important."— Presentation transcript:

1 What are the Odds? Sampling Theory and Logic

2 Let’s Be Realistic… It’s unlikely you’ll be in a position to do much sampling in your daily work Important to know sampling theory when consuming research

3 The Logic of Probability The universe and the sample The theoretical distribution curve (bell- shaped curve)  random distribution about the mean Mean and standard deviation, true and sample  Natural variation of the sample mean about the true mean

4 Random Samples “Equal chance of being chosen” Sample size Simple random sampling  Random number generation (p. 681)  Systematic random sampling (kth sampling)

5 Stratified Sampling Breaks the cardinal rule: unequal chance of being chosen In social work, interested in minority opinion Disproportionate stratified sampling captures minority voice “Stratify for variables of interest, randomize the rest”

6 Strategies for Stratification Divide population into homogeneous subgroups of interest Disproportionate stratification  Sample based on subgroup size: simple random or systematic (p. 269)  Simple oversampling  Must not generalize to larger population

7 Gender and Cultural Bias “When one group is the norm, the other group is the deviant” Systematic vs. random errors Source of systematic errors  Population frame bias  Insufficient sample size  Generalization errors – up and down “Stratify variables of interest, randomize the rest”

8 Non-random Sampling Convenience or availability sampling Purposive sampling Snowball sampling Quota sampling


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