```{r}
library(pwr)

# based on the difference observed in the previous study
pwr.t.test(d=(-0.2-(-0.55))/1.5,
           power=0.8,
           sig.level=0.05,
           type="two.sample",
           alternative="greater")
```


At least 228 subjects per condition. However, note that an additional criterion was reaching a specific estimation precision (defined as a maximum width of the 95 CIs around the group means.). Another was that equally many subjects were supposed to be in each condition:

(1) no 95\%CI of the means should be wider than $0.5$ points on the rating scale and 

(2) all conditions should have the same number of subjects. Both additional criteria were reached after $n~=240$ subjects, which terminated the data collection.    

 These criteria were fulfilled with $n~=240$ subjects in each condition, which terminated data collection.