precsize {designsize} | R Documentation |

## Sample size determination using power and precision analysis

### Description

It determines the ratio between the sample size of power analysis and precision analysis analysis and also, give the required sample sizes.

### Usage

```
precsize(pR, pT, sigr, sigt, c, alpha, beta)
```

### Arguments

`pR` |
Incidence rate for the reference group |

`pT` |
Incidence rate for the test group |

`sigr` |
Variability in the reference group |

`sigt` |
Variability in the test group |

`c` |
Constant value for allowance of maximum error margin |

`alpha` |
Level of significance |

`beta` |
The probability of type-II error |

### Details

A pre-study power analysis for sample size determination is usually performed to calculate an appropriate sample size for achieving a desired power for detecting a clinically meaningful difference at a prespecified level of significance. In practice, a much larger sample size is expected for detecting a relatively smaller difference, especially for clinical trials with extremely low incidence rate. As a result, sample size determination based on power analysis may not be feasible. So, it is a good suggestion to determine the sample size based on precision analysis.

### Value

precsize returns 3 values:

- R
Ratio between the sample size of power analysis and precision analysis

- n.power
Sample size required for power analysis

- n.precision
Sample size required for precision analysis

### Author(s)

Atanu Bhattacharjee, Rajashree Dey ,Soutik Halder and Akash Pawar

### See Also

ABdesign crt.match crt.unmatch phsize prsize crsize

### Examples

```
# The incidence rate of reference group is pR = 0.8 per thousands and that of test group
# is pT = 0.7 per thousands. It is also assumed that the respective stanadard deviation
# of reference and test group are sigr = 2 and sigt = 1 respectively. The constant value
# is chosen c = 0.08 to allow the maximum marginal error. The level of significance is
# alpha = 0.05 and the probability of type-II error is beta = 0.20.
precsize(pR = 0.8, pT = 0.7, sigr = 2, sigt = 1, c = 0.08, alpha = 0.05, beta = 0.20)
```

*designsize*version 0.1.0 Index]