UWorld Flashcards
Type II Error definition
The failure to detect a difference between groups when one really exists.
The Probability of a Type II Error (β) is relate to what?
Power
How is Power calculated?
Power = 1 - β
What does Increasing/Decreasing the sample size do to the Power?
Increasing sample size Increases Power. Decreasing sample size Decreases Power.
What does Increasing/Decreasing the sample size do to the Probability of a Type II Error (β)?
Increasing sample size Decreases β. Decreasing sample size Increases β.
DEFINITION:
The ability to detect a difference in the outcome of interest between 2 groups, if such a difference exists.
POWER
What is 1.) the Null Hypothesis and 2.) the Goal, of Superiority Trials?
- Null Hypothesis - the EFFECTS of the Drugs being compared are SIMILAR.
- Goal - to show that the New Drug is DIFFERENT (better; not unacceptably worse) than the comparator.
RELATIVE RISK (RR):
What are the Definition and Equation?
Relative Risk (RR) - a risk ratio comparing the Risk of an Outcome among the Exposed to that of the Unexposed.
RR = Risk of Exposed ÷ Risk of Unexposed):
RR = (a / a + b) ÷ (c / c + d)
ATTRIBUTABLE RISK PERCENTAGE (ARP or AR%):
What are the Definition and Equation?
Attributable Risk Percentage (ARP) - a measure of excess risk and estimates the proportion of disease among Exposed subjects that is attributed to Exposed Status.
If you don’t have Relative Risk:
ARP = Risk in Exposed - Risk in Unexposed x 100
Risk in Exposed
or
ARP = AR x 100
If you do have Relative Risk (RR):
ARP = (RR - 1) x 100
RR
POPULATION ATTRIBUTABLE RISK PERCENTAGE (PARP or PAR%):
What are the Definition and Equation?
PARP - the measure of excess risk in the Total Population (not only in exposed):
PARP = Risk in Total Population - Risk in Unexposed x 100
Risk in Total Population
Risk in Total Population = (Re)(Pe) + (Ru)(Pu)
** R = Risk; P = Proportion; e = exposed; u = unexposed **
OR
PARP = (Prevelance)(RR - 1) x 100
(Prevelance)(RR - 1) + 1
