Wrong results using ANOVA with repeated measures
Hello everybody, I did an experiment and I need to understand how to detect, by means of an ANOVA (repeated measures), the differences between males and females evaluations at stimulus level.
In the experiment, participants had to evaluate 7 stimuli in 2 conditions (EXP1 and EXP2). The structure of the table is the following: subject, stimulus, condition, sex, response. The design is the following:
- sex is a between-subjects factor (with two levels)
- stimulus is a within-subjects factor (with 3 assumed levels)
- condition is a within-subjects factor (with 2 levels)
- all factors are fully crossed
For example now I want to detect the difference between males and females evaluation for stimulus 1. So far the only way that I found is to use a t-test.
I used the following R command for conducting the ANOVA:
aov1 = aov(response ~ sex*stimulus*condition + Error(subject/(stimulus*condition)), data=scrd) summary(aov1)
but I don´t see the way to understand if evaluataions between males and females for stimulus 1 are significant. I can only see if there is a difference at global level between males and females for all the stimuli. But I am interested in discovering it for each stimulus.
How can I reach this goal?....I don´t think that the interactions of the previous ANOVA code can help me.
I used the t-test in this way
table_gravel_M <- subset(my_table, stimulus == "gravel" & sex == "M") table_gravel_F <- subset(my_table, stimulus == "gravel" & sex == "F") t.test(table_gravel_M$response,table_gravel_F$response)
Thanks in advance
Here an example of the table I used:
subject stimulus condition sex response subject1 gravel EXP1 M 59.8060 subject2 gravel EXP1 M 49.9880 subject3 gravel EXP1 M 73.7420 subject4 gravel EXP1 M 45.5190 subject5 gravel EXP1 M 51.6770 subject6 gravel EXP1 M 42.1760 subject7 gravel EXP1 M 56.1110 subject8 gravel EXP1 M 54.9500 subject9 gravel EXP1 M 62.6920 subject10 gravel EXP1 M 50.7270 subject1 gravel EXP2 M 70.9270 subject2 gravel EXP2 M 61.3200 subject3 gravel EXP2 M 70.2930 subject4 gravel EXP2 M 49.9880 subject5 gravel EXP2 M 69.1670 subject6 gravel EXP2 M 62.2700 subject7 gravel EXP2 M 70.9270 subject8 gravel EXP2 M 63.6770 subject9 gravel EXP2 M 72.4400 subject10 gravel EXP2 M 58.8560 subject11 gravel EXP1 F 46.5750 subject12 gravel EXP1 F 58.1520 subject13 gravel EXP1 F 57.4490 subject14 gravel EXP1 F 59.8770 subject15 gravel EXP1 F 55.5480 subject16 gravel EXP1 F 46.2230 subject17 gravel EXP1 F 63.3260 subject18 gravel EXP1 F 60.6860 subject19 gravel EXP1 F 59.4900 subject20 gravel EXP1 F 52.6630 subject11 gravel EXP2 F 55.7240 subject12 gravel EXP2 F 66.4220 subject13 gravel EXP2 F 65.9300 subject14 gravel EXP2 F 61.8120 subject15 gravel EXP2 F 62.5160 subject16 gravel EXP2 F 65.5780 subject17 gravel EXP2 F 59.5600 subject18 gravel EXP2 F 63.8180 subject19 gravel EXP2 F 61.4250 ..... ..... ..... .....