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statpsych: Statistical Methods for Psychologists

statpsych implements confidence interval and sample size methods that are especially useful in psychological research. The methods can be applied in 1-group, 2-group, paired-samples, and multiple-group designs and to a variety of parameters including means, medians, proportions, slopes, standardized mean differences, standardized linear contrasts of means, plus several measures of correlation and association. The confidence intervals and sample size functions are applicable to single parameters as well as differences, ratios, and linear contrasts of parameters. The sample size functions can be used to approximate the sample size needed to estimate a parameter or function of parameters with desired confidence interval precision or to perform a variety of hypothesis tests (directional two-sided, equivalence, superiority, noninferiority) with desired power. For details, see: https://dgbonett.sites.ucsc.edu/.

Installation

You can install the currently-released version from CRAN with this R command:

install.packages("statpsych")

Alternatively, you can install the latest development version from GitHub with these R commands:

install.packages("devtools")
devtools::install_github("dgbonett/statpsych")

Feedback, issues, and contributions

Submit feedback, suggestions, and bugs to github here.

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Version

Install

install.packages('statpsych')

Monthly Downloads

617

Version

1.9.0

License

GPL-3

Issues

Pull Requests

Stars

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Repository

https://github.com/dgbonett/statpsych/

Homepage

https://dgbonett.github.io/statpsych/

Maintainer

Douglas G. Bonett

Last Published

January 13th, 2026

Functions in statpsych (1.9.0)

Confidence interval for a biserial-phi correlation

Confidence interval for a G-index of agreement

Bayesian credible interval for a semipartial correlation with a skeptical prior

Confidence interval for G-index difference in a 2-group design

ci.2x2.stdmean.mixed

Computes confidence intervals of standardized effects in a 2x2 mixed design

ci.agree.3rater

Computes confidence intervals for a 3-rater design with dichotomous ratings

ci.bayes.normal

Bayesian credible interval for a normal prior distribution

Bayesian credible interval for a Pearson or partial correlation with a skeptical prior

Bayesian credible interval for a proportion

ci.2x2.stdmean.ws

Computes confidence intervals of standardized effects in a 2x2 within-subjects design

Confidence interval for a coefficient of quartile variation

Confidence interval for a biserial correlation

Confidence interval for a 2-group Pearson correlation difference

Confidence intervals for conditional (simple) slopes in a linear model

Confidence interval for a Pearson or partial correlation

Confidence interval for a coefficient of dispersion

Confidence interval for a difference in dependent Pearson correlations

ci.condslope.log

Confidence intervals for conditional (simple) slopes in a logistic model

Fisher confidence interval

Confidence interval for a Cronbach reliability

Confidence interval for an indirect effect

Confidence interval for eta-squared

Confidence interval for an intraclass reliablity coefficient

Confidence interval for two kappa reliability coefficients

Confidence interval for a linear contrast of parameters in a between-subjects design

Confidence interval for Cramer's V

Confidence interval for a coefficient of variation

Confidence intervals for diversity indices

Confidence interval for a 2-group correlation difference

Confidence interval for a difference in Cronbach reliabilities in a 2-group design

Confidence interval for a linear contrast of general linear model parameters

ci.lc.stdmean.ws

Confidence interval for a standardized linear contrast of means in a within-subjects design

Confidence interval for a mean absolute deviation

ci.lc.mean.scheffe

Scheffe confidence interval for a linear contrast of means in a between-subjects design

Confidence interval for a linear contrast of proportions in a between- subjects design

ci.lc.median.bs

Confidence interval for a linear contrast of medians in a between-subjects design

ci.lc.prop.scheffe

Scheffe confidence interval for a linear contrast of proportions in a between-subjects design

Confidence interval for a paired-samples median difference

Confidence interval for a linear contrast of means in a between-subjects design

Confidence interval for a Mann-Whitney parameter

Confidence interval for a mean

Confidence interval for a mean with a finite population correction

Confidence interval for a 2-group median difference

Confidence interval for a mean absolute prediction error

Confidence interval for a proportion using inverse sampling

Confidence interval for a proportion with a finite population correction

Confidence intervals for generalized means

ci.pairs.prop.bs

Bonferroni confidence intervals for all pairwise proportion differences in a between-subjects design

Confidence interval for a paired-samples mean difference

Confidence intervals for point-biserial correlations

ci.random.anova

Confidence intervals for parameters of one-way random effects ANOVA

Confidence interval for a phi correlation

Confidence interval for a Poisson rate

Confidence interval for a ratio of dispersion coefficients in a 2-group design

Confidence interval for a 2-group proportion difference using inverse sampling

Confidence intervals for a proportion

Confidence interval for an unknown population size

ci.ratio.mad.ps

Confidence interval for a paired-samples MAD ratio

Confidence interval for a ratio of coefficients of variation in a 2-group design

Confidence intervals for positive and negative predictive values with retrospective sampling

ci.lc.stdmean.bs

Confidence interval for a standardized linear contrast of means in a between-subjects design

Confidence interval for a linear contrast of regression coefficients in multiple group regression model

Confidence interval for a paired-samples proportion difference

Confidence interval for an odds ratio

ci.ratio.mean.ps

Confidence interval for a paired-samples mean ratio

Confidence interval for a 2-group mean difference

Confidence interval for a median

ci.ratio.poisson2

Confidence interval for a ratio of Poisson rates in a 2-group design

Confidence interval for a 2-group ratio of standard deviations

Confidence interval for a 2-group mean ratio

Confidence interval for a 2-group proportion ratio

Confidence interval for a slope in a simple linear model

Confidence interval for the parameter of the one-sample sign test

ci.ratio.prop.ps

Confidence interval for a paired-samples proportion ratio

Confidence interval for a semipartial correlation

ci.slope.prop.bs

Confidence interval for a slope of a proportion in a single-factor experimental design with a quantitative between-subjects factor

Confidence interval for a 2-group ratio of mean absolute deviations

Confidence intervals for pairwise proportion differences of a multinomial variable

Confidence interval for a tetrachoric correlation

ci.ratio.median2

Confidence interval for a 2-group median ratio

ci.slope.mean.bs

Confidence interval for the slope of means in a one-factor experimental design with a quantitative between-subjects factor

ci.ratio.median.ps

Confidence interval for a paired-samples median ratio

Confidence interval for a 2-group proportion difference

ci.slope.median.bs

Confidence interval for the slope of medians in a one-factor experimental design with a quantitative between-subjects factor

Theil-Sen estimate and confidence interval for slope

Confidence intervals for a 2-group standardized mean difference

ci.stdmean.strat

Confidence intervals for a 2-group standardized mean difference with stratified sampling

etasqr.gen.2way

Generalized eta-squared estimates in a two-factor design

Upper confidence limit of a variance

Tukey-Kramer confidence intervals for all pairwise mean differences in a between-subjects design

Prediction interval for a sample proportion in a future study

Confidence interval for an exponentiated slope

Approximates the power of a paired-samples t-test for a planned sample size

power.lc.mean.bs

Approximates the power of a test for a linear contrast of means for planned sample sizes in a between-subjects design

Indices of qualitative variation

Prediction interval for one score

Confidence intervals for generalized Yule coefficients

Approximates the power of a two-sample t-test for planned sample sizes

Confidence interval for a 2-group reliability difference

Confidence interval for a Spearman correlation

Confidence interval for a reliability coefficient

Confidence interval for a ratio of mean absolute prediction errors in a 2-group design

Confidence interval for a 2-group Spearman correlation difference

Confidence interval for a standardized mean

Bias adjustment for an eta-squared estimate

Approximates the power of a 1-group proportion test for a planned sample size

Generate a random sample

Approximates the power of a one-sample t-test for a planned sample size

Approximates the power of a test for equal correlations in a 2-group design for planned sample sizes

SEM fit indices

Parameter estimates for a signal detection study

Confidence interval for squared multiple correlation

Confidence intervals for a paired-samples standardized mean difference

Simulates confidence interval coverage probability for a Pearson correlation

Randomize a sample into groups

Generates random bivariate scores

Simulates confidence interval coverage probability for a Spearman correlation

sim.ci.stdmean.ps

Simulates confidence interval coverage probability for a standardized mean difference in a paired-samples design

Generate random sample of scores

size.ci.ancova2

Sample size for a 2-group ANCOVA confidence interval

Sample size for biserial-phi correlation confidence interval

Confidence interval for a standard deviation

Prediction limits for a sample variance in a future study

Approximates the power of a correlation test for a planned sample size

Prediction interval for difference of scores in a 2-level within-subjects experiment

Prediction interval for a difference of scores in a 2-group experiment

Simulates confidence interval coverage probability for a median

Simulates confidence interval coverage probability for a 2-group mean difference

Sample size for a G-index confidence interval

size.ci.cronbach2

Sample size for a 2-group Cronbach reliability difference confidence interval

sim.ci.stdmean2

Simulates confidence interval coverage probability for a standardized mean difference in a 2-group design

sim.ci.median.ps

Simulates confidence interval coverage probability for a median difference in a paired-samples design

Prediction limits for a sample correlation in a future study

Sample size for a coefficient of variation

size.ci.cronbach

Sample size for a Cronbach reliability confidence interval

Simulates confidence interval coverage probability for a median difference in a 2-group design

size.ci.cronbach.prior

Sample size for a Cronbach reliability confidence interval using an reliability estimate from a prior study

size.ci.lc.stdmean.bs

Sample size for a between-subjects standardized linear contrast of means confidence interval

size.ci.lc.prop.bs

Sample size for a between-subjects proportion linear contrast confidence interval

Sample size for a intraclass correlation confidence interval

size.ci.icc.prior

Sample size for an intraclass correlation confidence interval using a planning value from a prior study

Sample size for a confidence interval for the difference of any type of parameter

Prediction limits for sample value of Cronbach reliability in a future study

Sample size for an eta-squared confidence interval

size.ci.lc.median.bs

Sample size for a between-subjects median linear contrast confidence interval

size.ci.lc.mean.ws

Sample size for a within-subjects mean linear contrast confidence interval

Sample size for a median confidence interval

Sample size for a confidence interval for any type of parameter

size.ci.lc.stdmean.ws

Sample size for a within-subjects standardized linear contrast of means confidence interval

Sample size for a mean absolute prediction error confidence interval

size.ci.mean.ps

Sample size for a paired-samples mean difference confidence interval

size.ci.indirect

Sample size for an indirect effect confidence interval

size.ci.median2

Sample size for a 2-group median difference confidence interval

size.ci.oddsratio

Sample size for an odds ratio confidence interval

Sample size for a point-biserial correlation confidence interval

size.ci.prop.prior

Sample size for a proportion confidence interval using an estimated proportion from a prior study

Sample size for a 2-group proportion difference confidence interval

Sample size for a second-stage confidence interval

Sample size for a standard deviation confidence interval

Sample size for a 2-group mean difference confidence interval

Sample size for a mean confidence interval

Sample size for a squared multiple correlation confidence interval

size.ci.ratio.prop2

Sample size for a 2-group proportion ratio confidence interval

size.ci.mean.prior

Sample size for a mean confidence interval using an estimated variance from a prior study

Sample size for a Spearman correlation confidence interval

size.ci.slope.gen

Sample size for a slope confidence interval in a general statistical model

Sample size for a slope confidence interval

size.ci.ratio.mean.ps

Sample size for a paired-samples mean ratio confidence interval

Sample size for a 2-group Spearman correlation difference confidence interval

Approximates the power of a paired-samples test of equal proportions for a planned sample size

Simulates confidence interval coverage probability for a mean

Approximates the power of a 2-group proportion test for planned sample sizes

Sample size for a tetrachoric correlation confidence interval

Sample size for a Yule's Q confidence interval

size.equiv.mean.ps

Sample size for a paired-samples mean equivalence test

Sample size for a test of a Pearson or partial correlation

size.equiv.mean2

Sample size for a 2-group mean equivalence test

size.ci.prop.ps

Sample size for a paired-sample proportion difference confidence interval

size.supinf.mean.ps

Sample size for a paired-samples mean superiority or noninferiority test

size.interval.cor

Sample size for an interval test of a Pearson or partial correlation

size.equiv.prop.ps

Sample size for a paired-samples proportion equivalence test

size.ci.condmean

Sample size for a conditional mean confidence interval

Sample size for a Pearson or partial correlation confidence interval

size.ci.cor.prior

Sample size for a Pearson correlation confidence interval using an estimated correlation from a prior study

Simulates confidence interval coverage probability for a paired-samples mean difference

size.equiv.prop2

Sample size for a 2-group proportion equivalence test

Sample size for a 2-group Pearson correlation difference confidence interval

size.ci.lc.ancova

Sample size for a linear contrast confidence interval in an ANCOVA

Sample size for a test of 2-group difference for any type of parameter

size.supinf.mean2

Sample size for a 2-group mean superiority or noninferiority test

size.ci.lc.mean.bs

Sample size for a between-subjects mean linear contrast confidence interval

Sample size for a test of a mean

Sample size for a test of equal Pearson or partial correlation in a 2-group design

size.supinf.prop.ps

Sample size for a paired-samples superiority or inferiority test of proportions

size.test.cronbach

Sample size to test a Cronbach reliability

Sample size for a test of any type of parameter

Sample size for a Mann-Whitney test

size.ci.ratio.mean2

Sample size for a 2-group mean ratio confidence interval

Sample size for phi correlation confidence interval

Sample size for a proportion confidence interval

size.test.lc.mean.ws

Sample size for a test of a within-subjects mean linear contrast

size.ci.ratio.prop.ps

Sample size for a paired-samples proportion ratio confidence interval

size.ci.stdmean.ps

Sample size for a paired-samples standardized mean difference confidence interval

size.test.cronbach2

Sample size to test equality of Cronbach reliability coefficients in a 2-group design

Sample size for a test of a single proportion

size.test.prop.ps

Sample size for a test of a paired-samples proportion difference

size.test.mean.ps

Sample size for a test of a paired-samples mean difference

size.test.lc.prop.bs

Sample size for a test of between-subjects proportion linear contrast

size.test.mean2

Sample size for a test of a 2-group mean difference

Computes p-value for test of skewness

size.test.lc.ancova

Sample size for a mean linear contrast test in an ANCOVA

size.test.sign.ps

Sample size for a paired-samples sign test

size.test.slope

Sample size for a test of a slope

test.mono.mean.bs

Test of a monotonic trend in means for an ordered between-subjects factor

Hypothesis test for a mean

size.test.lc.mean.bs

Sample size for a test of a between-subjects mean linear contrast

Hypothesis test for a 2-group Pearson or partial correlation difference

size.ci.stdmean2

Sample size for a 2-group standardized mean difference confidence interval

Hypothesis test for a Spearman correlation

Computes p-value for test of excess kurtosis

test.mono.median.bs

Test of a monotonic trend in medians for an ordered between-subjects factor

test.mono.prop.bs

Test of monotonic trend in proportions for an ordered between-subjects factor

Hypothesis test for a paired-samples proportion difference

Hypothesis test for a 2-group proportion difference

Contrast coefficients for the slope of a quantitative factor

Hypothesis test for a Pearson or partial correlation

Between-subjects F statistic and eta-squared from summary information

Computes the reliability of a scale with r2 measurements given the reliability of a scale with r1 measurements

size.test.ancova2

Sample size for a 2-group ANCOVA hypothesis test

size.supinf.prop2

Sample size for a 2-group superiority or inferiority test of proportions

Sample size for a 1-group sign test

Hypothesis test of equal proportions in a between-subjects design

Hypothesis test for a 2-group Spearman correlation difference

size.test.prop2

Sample size for a test of a 2-group proportion difference

Hypothesis test for a proportion

Adjusted standard errors for slope coefficients in an exploratory analysis

ci.2x2.prop.mixed

Computes tests and confidence intervals of effects in a 2x2 mixed design for proportions

ci.2x2.mean.mixed

Computes tests and confidence intervals of effects in a 2x2 mixed design for means

ci.2x2.median.mixed

Computes confidence intervals in a 2x2 mixed design for medians

ci.2x2.stdmean.bs

Computes confidence intervals of standardized effects in a 2x2 between-subjects design

ci.2x2.median.bs

Computes tests and confidence intervals of effects in a 2x2 between-subjects design for medians

ci.2x2.median.ws

Computes confidence intervals of effects in a 2x2 within-subjects design for medians

Computes tests and confidence intervals of effects in a 2x2 between-subjects design for means

Computes tests and confidence intervals of effects in a 2x2 between- subjects design for proportions

Computes tests and confidence intervals of effects in a 2x2 within-subjects design for means