blindrecalc facilitates the planning of a clinical trial with an internal pilot study and blinded sample size recalculation.

Install the current CRAN version of blindrecalc with:

```
install.packages("blindrecalc")
```

Or install the development version from GitHub with:

```
# install.packages("devtools")
devtools::install_github("imbi-heidelberg/blindrecalc")
```

blindrecalc currently supports continuous and binary endpoints for
superiority and non-inferiority test problems. Continuous endpoints are
analyzed using Studentâ€™s t-test, binary endpoints are analyzed using the
Chi-squared test for superiority trials and the Farrington-Manning test
for non-inferiority trials. Each design can be defined using a
setup-function: `setupStudent`

, `setupChiSquare`

and
`setupFarringtonManning`

. For example, to setup a superiority trial with
a continuous endpoint:

```
library(blindrecalc)
design <- setupStudent(alpha = 0.025, beta = 0.2, r = 1, delta = 5)
```

`alpha`

and `beta`

refer to the type 1 and type 2 error rate, `r`

is the
sample size allocation ratio and `delta`

is the effect size between the
null and the alternative hypothesis. For a non-inferiority trial with a
shifted t-test, additionally the argument `delta_NI`

must be specified.

To calculate the sample size for a fixed design, use `n_fix`

:

```
n_fix(design, nuisance = c(5, 10, 15))
#> [1] 31.39552 125.58208 282.55967
```

`nuisance`

refers to the nuisance parameter of the design, which in the
case of the t-test is the common variance of the outcome variable.

To calculate the type 1 error rate of the design using blinded sample
size recalculation, use `toer`

:

```
toer(design, n1 = c(30, 60, 90), nuisance = 10, recalculation = TRUE)
#> [1] 0.0259 0.0235 0.0252
```

`n1`

refers to the sample size of the internal pilot study
`recalculation = TRUE`

specifices that the type 1 error rate for a
design with blinded sample size recalculation should be computed.

To compute the power of the design, use `pow`

:

```
pow(design, n1 = c(30, 60, 90), nuisance = 10, recalculation = TRUE)
#> [1] 0.7877 0.8039 0.8056
```

To calculate the distribution of the total sample sizes use `n_dist`

:

```
n_dist(design, n1 = c(30, 60, 90), nuisance = 10)
#> n_1 = 30 n_1 = 60 n_1 = 90
#> Min. : 36.0 Min. : 63 Min. : 90.0
#> 1st Qu.:109.0 1st Qu.:117 1st Qu.:120.0
#> Median :131.0 Median :132 Median :133.0
#> Mean :134.1 Mean :134 Mean :134.5
#> 3rd Qu.:155.0 3rd Qu.:150 3rd Qu.:147.0
#> Max. :322.0 Max. :282 Max. :223.0
```

A paper describing blindrecalc can be found here.

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