Sample size for a second-stage confidence interval

Computes the second-stage sample size required to obtain desired confidence interval precision. This function can use either the total sample size for all groups in the first stage sample or a single group sample size in the first stage sample. If the total first-stage sample size is given, then the function computes the total sample size required in the second-stage sample. If a single group first-stage sample size is given, then the function computes the single-group sample size required in the second-stage sample. The second-stage sample is combined with the first-stage sample to obtain the desired confidence interval width.

Usage

size.ci.second(n0, w0, w)

Arguments

n0

first-stage sample size

w0

confidence interval width in first-stage sample

w

desired confidence interval width

Value

Returns the required sample size for the second-stage sample

Examples

size.ci.second(20, 5.3, 2.5)
#>  Second-stage sample size
#>                        70

# Should return:
# Second-stage sample size
#                       70