I am struggling to interpret my output in R. It does not make sense to me.
I first regressed participants' ratings (= value
) on manipulations (= variable
: H high, AI high, H low, AI low, and control). I then checked whether this effect is moderated by the participants' experience (= Frequency
:7 groups, the higher, the less experience). Frequency was added as an interaction factor in my model:
H4_mod <- lmer(value ~ variable * Frequency + (1|subject), data =
ANALYSIS_long, REML = FALSE)
Then, in order to find out whether the interaction effect is statistically significant, I compared the H4_mod
with a reduced model:
red_H4_mod <- lmer(value ~ variable + Frequency + (1|subject), data =
ANALYSIS_long, REML = FALSE)
An ANOVA and a look at cAICs revealed that the interaction is statistically significant. So far, so good.
Now, I want to find out what the effect looks like. I predicted that the higher the experience, the lower the effect of the prediction (value ~ variable).
I get confused with the output I get from
summary(H4_mod)
Fixed effects:
Estimate Std. Error df t value Pr(>|t|)
(Intercept) 6.846e+00 2.872e-01 8.334e+02 23.839 < 2e-16 ***
variable[T.2] 9.542e-01 3.223e-01 1.032e+03 2.960 0.003145 **
variable[T.3] -8.000e-01 3.223e-01 1.032e+03 -2.482 0.013226 *
variable[T.4] 1.104e+00 3.223e-01 1.032e+03 3.426 0.000638 ***
variable[T.5] -1.154e+00 3.223e-01 1.032e+03 -3.581 0.000359 ***
Frequency2 3.310e-01 3.739e-01 8.334e+02 0.885 0.376362
Frequency3 5.490e-01 3.650e-01 8.334e+02 1.504 0.132893
Frequency4 -5.164e-01 5.615e-01 8.334e+02 -0.920 0.358013
Frequency5 2.875e-01 6.421e-01 8.334e+02 0.448 0.654468
Frequency6 5.417e-02 6.043e-01 8.334e+02 0.090 0.928602
Frequency7 -1.156e+00 5.295e-01 8.334e+02 -2.183 0.029329 *
variable[T.2]:Frequency2 -3.397e-01 4.197e-01 1.032e+03 -0.809 0.418551
variable[T.3]:Frequency2 -4.087e-01 4.197e-01 1.032e+03 -0.974 0.330432
variable[T.4]:Frequency2 -5.592e-01 4.197e-01 1.032e+03 -1.332 0.183033
variable[T.5]:Frequency2 -2.545e-01 4.197e-01 1.032e+03 -0.606 0.544378
variable[T.2]:Frequency3 -5.901e-01 4.097e-01 1.032e+03 -1.440 0.150082
variable[T.3]:Frequency3 5.128e-03 4.097e-01 1.032e+03 0.013 0.990015
variable[T.4]:Frequency3 -4.837e-01 4.097e-01 1.032e+03 -1.181 0.238045
variable[T.5]:Frequency3 2.875e-01 4.097e-01 1.032e+03 0.702 0.482980
variable[T.2]:Frequency4 3.407e-02 6.303e-01 1.032e+03 0.054 0.956904
variable[T.3]:Frequency4 2.471e-01 6.303e-01 1.032e+03 0.392 0.695154
variable[T.4]:Frequency4 2.841e-01 6.303e-01 1.032e+03 0.451 0.652301
variable[T.5]:Frequency4 1.025e+00 6.303e-01 1.032e+03 1.626 0.104285
variable[T.2]:Frequency5 -5.708e-01 7.208e-01 1.032e+03 -0.792 0.428548
variable[T.3]:Frequency5 -2.250e+00 7.208e-01 1.032e+03 -3.122 0.001848 **
variable[T.4]:Frequency5 -1.288e+00 7.208e-01 1.032e+03 -1.786 0.074342 .
variable[T.5]:Frequency5 -1.413e+00 7.208e-01 1.032e+03 -1.960 0.050295 .
variable[T.2]:Frequency6 -1.970e-01 6.783e-01 1.032e+03 -0.290 0.771525
variable[T.3]:Frequency6 -9.714e-01 6.783e-01 1.032e+03 -1.432 0.152417
variable[T.4]:Frequency6 -3.327e-01 6.783e-01 1.032e+03 -0.491 0.623863
variable[T.5]:Frequency6 -1.203e+00 6.783e-01 1.032e+03 -1.773 0.076448 .
variable[T.2]:Frequency7 3.658e-01 5.944e-01 1.032e+03 0.616 0.538350
variable[T.3]:Frequency7 -6.000e-02 5.944e-01 1.032e+03 -0.101 0.919610
variable[T.4]:Frequency7 2.583e-02 5.944e-01 1.032e+03 0.043 0.965340
variable[T.5]:Frequency7 4.742e-01 5.944e-01 1.032e+03 0.798 0.425178
---
Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
Can someone explain it to me? The intercept is my control manipulation ("variable"), but what happened to Frequency 1? I read that only the Frequency 7 group has a significant impact on the relationship (value ~ variable). When I look further down at the (what I think) actual interaction effects, these are only significant for Frequency 5.
Furthermore, I tried to figure out the relationships by looking at an effects plot
e <- allEffects(H4_mod)
plot(e, multiline = TRUE, confint = TRUE, ci.style = "bars")
Unfortunately, this confuses me even more... Can someone help me interpreting the results? So far, I can only say that Frequency significantly interacts with the value ~ variable relationship. But I would love (and have) to make a statement about the direction.
THANK YOU!