Equations Flashcards
Maintenance dose
=(Cp * CL * time) / F
Loading dose
=(Cp * Vd ) / F
Volume of distribution
Vd = (total amount in body) / (Cp)
Half life
= (0.69 * Vd ) / CL
Clearance
= (Rate of elimination) / Cp = Vd * Ke
Sensitivity
=Proportion with disease test +.
= TP / (TP + FN)
=1 - FN rate
Rule out.
Specificity
=Proportion that test neg without disease.
= TN / (TN + FP)
=1 - FP rate
Positive predictive value
= TP / (TP + FP)
Varies directly with prevalence.
Negative predictive value
= TN / (TN + FN).
Varies inversely with prevalence.
Odds raio (OR)
= (odds that group with disease was exposed to risk factor) / (odds that the group without disease was exposed)
Relative risk (RR)
= (risk of developing dz if exposed) / (risk if not exposed
If low prevalence, OR ~ RR
Attributable risk (AR)
= (risk if exposed) - (risk unexposed)
Looks at adverse events.
e.g. risk of lung cancer in smoker = 21%, non-smoker 1%, then 20% attributable to smoking.
=(RR-1)/RR
Absolute risk reduction (ARR)
= (risk if exposed) - (risk unexposed)
Number needed to treat
= 1 / ARR
Number needed to harm
= 1 / AR
Standard error of the mean
= (standard deviation sigma) / sqr(n)
Normal distribution
Mean = median = mode
1 sigma = 68%
2 sigma = 95%
3 sigma = 99.7%
Type I Error (alpha)
= False-positive error.
alpha = saw a difference that did not exist.
Type II Error (beta)
= False-negative error.
beta = blind to a difference that did exist.
Confidence Interval
= range from [mean - Z(SEM)] to [mean + Z(SEM)]
Power
Power = 1 - beta
Relative risk reduction (RRR)
= (risk of control - risk of treatment) / risk of control
=1-RR
