Issues in Randomization Outline

Vocabulary• Y i = β 0 + β 1 x 1i + ε i• Y = outcome or response variable– Might not be an actual response• X = covariate, variable• β 0 = intercept– Average value of Y when X = 0• β 1 = slope, coefficient• ε = error, residual, difference betweensample fit or prediction and personY i = β 0 + β 1 x 1i + ε i• Subscript ‘i’ is person i; i = 15– Y 15 = 119 (SBP); x 15 = 1 (on treatment)• Y = β 0 + β 1 x 1 general sample model– Say β 0 = 150, β 1 = -20• Y 15 = β 0 + β 1 x 15 + ε 15– Thus 119 = 150 – 20*1 + ε 15– So ε 15 = 119 – 150 + 20 = -11– Difference between Y 15 and modelpredicted Y 15 = -11Vocabulary• Statistic: Compute from sample• Sampling Distribution– All possible values statistic can have– Samples of a given size randomly drawnfrom the same population• Parameter: Compute from population– Usually unknown to researcher– Several large studies in population26