| 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. 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
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