# Free statistical calculators

## Test for one proportion calculator

## Computational notes

### P-value

The significance level, or P-value, is calculated using a general z-test (Altman, 1991):

where *p* is the observed proportion; *p*_{exp} is the Null hypothesis (or expected) proportion; and *se*(*p*) is the standard error of the expected proportion:

The P-value is the area of the normal distribution that falls outside ±*z* (see Values of the Normal distribution table).

### Confidence interval

MedCalc calculates the "exact" Clopper-Pearson confidence interval for the observed proportion (Clopper & Pearson, 1934; Fleis et al., 2003).

## Literature

- Altman DG (1991) Practical statistics for medical research. London: Chapman and Hall.
- Clopper C, Pearson ES (1934) The use of confidence or fiducial limits illustrated in the case of the binomial. Biometrika 26:404–413.
- Fleiss JL, Levin B, Paik MC (2003) Statistical methods for rates and proportions, 3
^{rd}ed. Hoboken: John Wiley & Sons. (p. 26) Book info

## External links

- Binomial proportion confidence interval on Wikipedia.