statpsych (version 2.0.0)

ci.mean2: 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)

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

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

References

Snedecor1980statpsych

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