statpsych (version 1.7.0)

ci.2x2.mean.bs: Computes tests and confidence intervals of effects in a 2x2 between-subjects design for means

Description

Computes confidence intervals and tests for the AB interaction effect, main effect of A, main effect of B, simple main effects of A, and simple main effects of B in a 2x2 between-subjects design with a quantitative response variable. A Satterthwaite adjustment to the degrees of freedom is used and equality of population variances is not assumed.

Usage

ci.2x2.mean.bs(alpha, y11, y12, y21, y22)

Value

Returns a 7-row matrix (one row per effect). The columns are:

• Estimate - estimate of effect

• 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

Arguments

alpha

alpha level for 1-alpha confidence

y11

vector of scores at level 1 of A and level 1 of B

y12

vector of scores at level 1 of A and level 2 of B

y21

vector of scores at level 2 of A and level 1 of B

y22

vector of scores at level 2 of A and level 2 of B

Examples

y11 <- c(14, 15, 11, 7, 16, 12, 15, 16, 10, 9)
y12 <- c(18, 24, 14, 18, 22, 21, 16, 17, 14, 13)
y21 <- c(16, 11, 10, 17, 13, 18, 12, 16, 6, 15)
y22 <- c(18, 17, 11, 9, 9, 13, 18, 15, 14, 11)
ci.2x2.mean.bs(.05, y11, y12, y21, y22)

# Should return:
#          Estimate       SE           t       df           p         LL         UL
# AB:         -5.10 2.224860 -2.29227953 35.47894 0.027931810 -9.6145264 -0.5854736
# A:           1.65 1.112430  1.48323970 35.47894 0.146840430 -0.6072632  3.9072632
# B:          -2.65 1.112430 -2.38217285 35.47894 0.022698654 -4.9072632 -0.3927368
# A at b1:    -0.90 1.545244 -0.58243244 17.56296 0.567678242 -4.1522367  2.3522367
# A at b2:     4.20 1.600694  2.62386142 17.93761 0.017246053  0.8362274  7.5637726
# B at a1:    -5.20 1.536952 -3.38331916 17.61093 0.003393857 -8.4341379 -1.9658621
# B at a2:    -0.10 1.608657 -0.06216365 17.91650 0.951120753 -3.4807927  3.2807927