SAMPLE SIZE AND POWER ANALYSIS
CALCULATOR AND GRAPHER
Health Decision Strategies, LLC.
Data Entry Page
--
Beta version, for demonstration only
-
-
Enter data in yellow boxes, hit "submit button" and answers will appear
on the next page in blue boxes -- graphs of data below.
WTP_1
WTP_2
WTP_3
WTP_4
WTP_5
WTP Threshold -->
Z (alpha/2)=
Z value for probability
<-- Prob of type I error (alpha)
or
Z (beta)=
Z value for probability of Type II error
<-- Prob of type II error (beta)
or
sdet=
standard deviation of the effect in treatment group
sdec=
standard deviation of the effect in control group
sdct=
standard deviation of the cost in treatment group
sdcc=
standard deviation of the cost in control group
dC=
mean difference in cost
dE=
mean difference in effect
Corr_dEdC
correlation between difference in cost and difference in effect
Sample Size Calculator - Results - number needed in each arm based on data entered above.
WTP_1
WTP_2
WTP_3
WTP_4
WTP_5
N =
Power Analysis
If the study has already been completed, this section below calculates the power to detect a difference, if a difference actually exists,
based on the numbers entered in the first group of yellow boxes above.
N_1
N_2
N_3
N_4
N_5
Study Sample
Size
1-Z_beta
Power = (prob(1-Z_beta))
Figure 1. Below is a graph example illustrating the data results generated by the HDS sample size calculator.This shows the sample size by willingness to pay and by different values of the correlation between cost and effect. Note the "effect only" line which is constant.
Figure 2. Below is a graph example illustrating the data results generated by the HDS sample size calculator.This shows the sample size by willingness to pay and by different values of power. Note the "effect only" line which is constant.
Figure 3. Below is a graph example illustrating the data results generated by the HDS power calculator.This shows the power by sample size for different values of the correlation between cost and effect.
References:
Briggs A and Gray A. Power and sample size calculations for stochastic
cost-effectiveness analysis. Med Decis Making 1998: 18 suppl:S81-S92.
Briggs A and Tambour M. The design and analysis of stochastic
cost-effectiveness studies for the evaluation of health care interventionsl.
Stockholm School of Economics. Working paper #234. April 1998.
Walter SD et al. Estimation, power and sample size calculations for
stochastic cost and effectiveness analysis. Pharmacoeconomics
2007; 25(6):455-466.
Glick H et al. Economic evaluation in clinical trials. Oxford University
Press, 2007.
The browser does not support JavaScript. The calculations created using
HDS
will not work. Please access the web page using another browser.