Description Usage Arguments Value References Examples
This function calculates the promising zone boundaries at an interim analysis of a
clinical trial
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r |
Proportion of subjects assigned to active group |
n1 |
Number of patients / events at first interim analysis (NULL if parameter f provided) |
n2 |
Number of patients / events at final analysis |
alpha_1s |
one-sided alpha |
eff_est |
effect observed/estimated at interim |
eff_planned |
planned effect (usually alternative hypothesis, but can be modified to obtain |
eff_null |
effect corresponding with null hypothesis (e.g. 1 for hazard rates, 0 for difference) |
SE |
standard error: has to be provided if type not equal to "HR". If for instance SE =1 |
p_c |
proportion in control group (needs to be provided if type="prop") |
sd_t |
standard deviation in treatment group (needs to be provided if type="cont") |
sd_c |
standard deviation in control group (needs to be provided if type="cont") |
type |
if type="HR", then SE is calculated, if type="general", then SE's have to be provided |
pow |
Power, needed to calculate sample size in second part provided to obtain given power |
f |
n1/n2 at interim analysis. Only to be provided if n1 and n2 not provided |
max |
(Maximum sample size)/(original sample size), could be for instance 1.5, 2 or 3 |
plot_effect |
TRUE if plotting boundaries with corresponding effect scale |
a list of three vectors
CP_obs : conditional power, given 1) observed effect at interim, 2) total sample size,
3) Assumed true effect= "eff_est" parameter
CP_planned : conditional power, given 1) observed effect at interim, 2) total sample size,
3) Assumed true effect= "eff_planned" parameter
n2_inc_new : additional patients needed to obtain given power
CP_ll lower boundary of promising zone (z-score, b-value, conditional power, effect scale)
CP_ul upper boundary of promising zone (z-score, b-value, conditional power, effect scale)
Lan and Wittes. The B-Value: A Tool for Monitoring Data. Biometrics 1988;44:579-585
Mehta CR, Pocock SJ. Adaptive increase in sample size when interim results are promising: A practical
guide with examples. Statist. Med. 2011;30:3267–3284
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