What should be in the protocol? Sample size justification Methods of calculation a Quantities used in calculation: ● Variances ● mean values e response rates difference to be detected
What should be in the protocol? ◼ Sample size justification ◼ Methods of calculation ◼ Quantities used in calculation: • Variances • mean values • response rates • difference to be detected
Realistic and conservative ■ Overestimated size: ■ unfeasible a early termination ■ Underestimated size justify an increase extension in follow-up a incorrect conclusion WORSE)
Realistic and Conservative ◼ Overestimated size: ◼ unfeasible ◼ early termination ◼ Underestimated size ◼ justify an increase ◼ extension in follow-up ◼ incorrect conclusion (WORSE)
What is a(type i error? The probability of erroneously rejecting the null hypothesis a ( Put an useless medicine into the market!)
What is (Type I error)? ◼ The probability of erroneously rejecting the null hypothesis ◼ (Put an useless medicine into the market!)
What is B(type Ii error)? a The probability of erroneously failing to reject the null hypothesis a(keep a good medicine away from patients!)
What is (Type II error)? ◼ The probability of erroneously failing to reject the null hypothesis. ◼ (keep a good medicine away from patients!)
What is power a Power quantifies the ability of the study to find true differences of various values ofδ ■ Power=1-β= P(accept H1|H1 1s true) ----the chance of correctly identify h1 (correctly identify a better medicine
What is Power ? ◼ Power quantifies the ability of the study to find true differences of various values of . ◼ Power = 1- =P (accept H1|H1 is true) ◼ ----the chance of correctly identify H1 (correctly identify a better medicine)