Power, Sample Size, Effect Size: Considerations for Research

power , Sample size , Effect size : Considerations for Research Carol B. Thompson JH Biostatistics Center SON Brown Bag November 20, 2012 Research Approaches Comparisons statistical hypotheses Estimates precision (confidence intervals) 3/1/2013 Thompson - power / Effect size 2 Population vs Research Views 3/1/2013 3 Thompson - power / Effect size Type I and Type II Errors (Which is Worse Risk?) 3/1/2013 4 Thompson - power / Effect size Related Parameters for Prospective Analysis Effect size Sample size power (1- ) 3/1/2013 Thompson - power / Effect size 5 Parameters for and 3/1/2013 6 Thompson - power / Effect size vs doesn t rely on any of the other parameters or power relies on 3 parameters (N, , ES) Which relate to a specific HA For same Sample size and ES, lower higher 3/1/2013 Thompson - power / Effect size 7 Comparing Two Means 3/1/2013 8 Thompson - power / Effect size Choosing power Level - 1 Underpowered study Waste resources; can t reject H0 Can misdirect future studies if results are NS Unethical if subjecting individual to inferior treatment Overpowered study Waste resources?

Power vs Precision •Related questions: –How much power to detect certain ES? –How precise should my estimate be? •ES impacts power, but no direct relation to accuracy/precision •Decide on study aim: comparison, estimate or both 3/1/2013 Thompson - Power/Effect Size 27

Loading..

Tags:

  Research, Power, Samples, Precision, Size, Effect, Considerations, Sample size, Considerations for research, Effect sizes

Information

Related search queries