ci.mean2 {statpsych} | R Documentation |
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.
ci.mean2(alpha, m1, m2, sd1, sd2, n1, n2)
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 |
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
Snedecor GW, Cochran WG (1989). Statistical Methods, 8th edition. ISU University Pres, Ames, Iowa.
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