ci.lc.mean.bs {statpsych} | R Documentation |
Computes a test statistic and confidence interval for a linear contrast of means. This function computes both unequal variance and equal variance confidence intervals and test statistics. A Satterthwaite adjustment to the degrees of freedom is used with the unequal variance method.
ci.lc.mean.bs(alpha, m, sd, n, v)
alpha |
alpha level for 1-alpha confidence |
m |
vector of estimated group means |
sd |
vector of estimated group standard deviations |
n |
vector of sample sizes |
v |
vector of betwen-subjects contrast coefficients |
Returns a 2-row matrix. The columns are:
Estimate - estimated linear contrast
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.
m <- c(33.5, 37.9, 38.0, 44.1) sd <- c(3.84, 3.84, 3.65, 4.98) n <- c(10,10,10,10) v <- c(.5, .5, -.5, -.5) ci.lc.mean.bs(.05, m, sd, n, v) # Should return: # Estimate SE t df # Equal Variances Assumed: -5.35 1.300136 -4.114955 36.00000 # Equal Variances Not Assumed: -5.35 1.300136 -4.114955 33.52169 # p LL UL # Equal Variances Assumed: 0.0002152581 -7.986797 -2.713203 # Equal Variances Not Assumed: 0.0002372436 -7.993583 -2.706417