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DMAR (version 1.0.0)

ci_sm: Confidence Interval for the Standardized Mean

Description

Computes the exact confidence interval for the standardized mean, the mean divided by the standard deviation, by inverting the noncentral t distribution. The standardized mean is the one-sample analog of the standardized mean difference and shares its noncentral interval theory.

Usage

ci_sm(
  sm = NULL,
  mean = NULL,
  sd = NULL,
  ncp = NULL,
  N = NULL,
  conf_level = 0.95,
  alpha_lower = NULL,
  alpha_upper = NULL,
  ...
)

Value

A 3-row data.frame with columns term and value. The term values are "lower_limit" (the lower confidence limit on the standardized mean), "std_mean" (the standardized mean), and "upper_limit" (the upper confidence limit).

Arguments

sm

Standardized mean

mean

Mean

sd

Standard deviation

ncp

Noncentral parameter

N

Sample size

conf_level

Confidence interval coverage (i.e., 1 - Type I error rate); default is .95

alpha_lower

Type I error for the lower confidence limit

alpha_upper

Type I error for the upper confidence limit

...

Allows one to potentially include parameter values for inner functions

Author

Ken Kelley [email protected]

Details

The user must specify the standardized mean in one and only one of the three ways: a) mean and standard deviation (mean and sd), b) standardized mean (sm), and c) noncentral parameter (ncp). The confidence level must be specified in one of following two ways: using confidence interval coverage (conf_level), or lower and upper confidence limits (alpha_lower and alpha_upper). This function uses the exact confidence interval method based on noncentral t-distributions. The confidence interval for noncentral t-parameter can be obtained from the ci_nc_t function in DMAR.

References

Kelley, K. (2007). Confidence intervals for standardized effect sizes: Theory, application, and implementation. Journal of Statistical Software, 20(8), 1--24. tools:::Rd_expr_doi("10.18637/jss.v020.i08")

Steiger, J. H., & Fouladi, R. T. (1997). Noncentrality interval estimation and the evaluation of statistical methods. In L. L. Harlow, S. A. Mulaik, & J. H. Steiger (Eds.), What if there were no significance tests? (pp. 221--257). Mahwah, NJ: Lawrence Erlbaum.

See Also

ci_nc_t

Other confidence intervals for effect sizes: ci_R2(), ci_c(), ci_c_ancova(), ci_c_ancova_bp(), ci_correlation, ci_cv(), ci_eta_squared(), ci_eta_squared_generalized(), ci_eta_squared_partial(), ci_mahalanobis(), ci_omega_squared(), ci_pvaf(), ci_rc(), ci_reg_coef(), ci_rmsea(), ci_sc(), ci_sc_ancova(), ci_smd(), ci_smd_c(), ci_snr(), ci_src(), ci_srsnr(), contrast_adjusted(), plot_smd()

Examples

Run this code
ci_sm(sm = 2.037905, N = 13, conf_level = .95)
ci_sm(mean = 30, sd = 14.721, N = 13, conf_level = .95)
ci_sm(ncp = 7.347771, N = 13, conf_level = .95)
ci_sm(sm = 2.037905, N = 13, alpha_lower = .05, alpha_upper = 0)
ci_sm(mean = 50, sd = 10, N = 25, conf_level = .95)

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