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.

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

Examples

ci.mean2(.05, 15.4, 10.3, 2.67, 2.15, 30, 20)

# Should return:
#                              Estimate       SE        t      df      
# Equal Variances Assumed:          5.1 1.602248 3.183029 48.0000 
# Equal Variances Not Assumed:      5.1 1.406801 3.625247 44.1137 
#                                          p       LL       UL
# Equal Variances Assumed:      0.0025578586 1.878465 8.321535
# Equal Variances Not Assumed:  0.0007438065 2.264986 7.935014

statpsych documentation built on Sept. 11, 2024, 7:42 p.m.