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Confidence interval with given upper bounds, time of tests, the last Z-value, and confidence level.
seqCI(bi, ti, Zval, conf.level=0.95)confidence interval of Z-value for the given confidence level.
upper bound z-values
times for test. These should be [0, 1].
the last z-value from the observed data. This is not necessarily the planned final Z-value.
confidence level
Kyun-Seop Bae k@acr.kr
It calculates confidence interval with given upper bounds, time of tests, the last Z-value, and confidence level. It assumes two-side test. mvtnorm::pmvt (with noncentrality) is better than pmvnorm in calculating power, sample size, and confidence interval. But, Lan-DeMets used multi-variate normal rather than multi-variate noncentral t distributionh. This function followed Lan-DeMets for the consistency with previous results. For the theoretical background, see the reference.
Reboussin DM, DeMets DL, Kim K, Lan KKG. Computations for group sequential boundaries using the Lan-DeMets function method. Controlled Clinical Trials. 2000;21:190-207.
seqCI(bi = c(2.53, 2.61, 2.57, 2.47, 2.43, 2.38),
ti = c(.2292, .3333, .4375, .5833, .7083, .8333), Zval=2.82)
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