| ci.mean2 {statpsych} | R Documentation |
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. 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 - p-value
LL - lower limit of the confidence interval
UL - upper limit of the confidence interval
References
Snedecor GW, Cochran WG (1989). Statistical Methods, 8th edition. ISU University Pres, Ames, Iowa.
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