ci.mean2: Confidence interval for a 2-group mean difference

In statpsych: Statistical Methods for Psychologists

Confidence interval for a 2-group mean difference

Description

Computes equal variance and unequal variance confidence intervals for a population 2-group mean difference using the estimated means, estimated standard deviations, and sample sizes. Also computes equal variance and unequal variance independent-samples t-tests. Use the t.test function for raw data input.

For more details, see Section 2.3 of Bonett (2021, Volume 1)

Usage

ci.mean2(alpha, m1, m2, sd1, sd2, n1, n2)

Arguments

alpha	alpha level for 1-alpha confidence
m1	estimated mean for group 1
m2	estimated mean for group 2
sd1	estimated standard deviation for group 1
sd2	estimated standard deviation for group 2
n1	sample size for group 1
n2	sample size for group 2

Value

Returns a 2-row matrix. The columns are:

• Estimate - estimated mean difference

• SE - standard error

• t - t test statistic

• df - degrees of freedom

• p - two-sided p-value

• LL - lower limit of the confidence interval

• UL - upper limit of the confidence interval

References

\insertRef

Snedecor1980statpsych

\insertRef

Bonett2021statpsych

Examples

ci.mean2(.05, 19.4, 11.3, 2.70, 2.10, 40, 40)
# Should return:
#                              Estimate        SE       t    df p
# Equal Variances Assumed:          8.1 0.5408327 14.9769 78.00 0
# Equal Variances Not Assumed:      8.1 0.5408327 14.9769 73.54 0
#                                    LL       UL
# Equal Variances Assumed:     7.023285 9.176715
# Equal Variances Not Assumed: 7.022256 9.177744

statpsych documentation built on Jan. 13, 2026, 1:07 a.m.