Sampling 5 1 Introduction ⚫ ⚫ ⚫ How we collect data is fundamental to criminal justice research Sampling – select observations ⚫ What is the best way to do this? Probability vs non-probability sampling Generalization ⚫ External validity – degree to which research findings generalize beyond the specific context in which they were studied ⚫ Generalization across participants ⚫ College students ⚫ Gender ⚫ Culture Probability sampling ⚫ What is probability sampling? ⚫ Why use? ⚫ Want to represent the larger population ⚫ We want to generalize to the larger population ▪ US Census – the goal is to capture the entire population, but this rarely happens 4 Sampling bias ⚫ ⚫ Bias: not typical / not representative Bias: personal bias 5 Representativeness & Probability of selection ⚫ Basic principle of probability sampling ⚫ All elements (e.g., persons, households) in the population have some opportunity of being included in the sample, and the mathematical probability that any one of them will be selected can be calculated – it’s definable 6 Probability theory and sampling distribution ⚫ ⚫ Population ⚫ Population parameter Sample statistic 7 Probability theory and sampling distribution ⚫ ⚫ ⚫ Sampling distribution ⚫ http://onlinestatbook.com/stat_sim/sampling_dist/index.h tml The sampling distribution is the range of sample statistics that would be obtained if we selected many samples Sampling error ...
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