We conducted a study where we are measuring perceived tiredness at different intervals (a total of 10). We recorded a score before starting the experiment, as a covariate to account for differences in baseline (i.e. different people would have started at different levels of tiredness).
The experiment asked them to do a single task (keep pressing a button occurring at a random location on a smartphone). After every 1 minute, the activity (smartphone app) paused, and the participants were asked to give a score between 0-10 for their perceived tiredness. The activity ran for 10 minutes and thus we have 10 scores for each subject (plus 1 for the baseline).
I want to compare the effect of the condition (treatment) between all the participants (within-subject).
Now, ANCOVA is good for adjusting pre-treatment scores (i.e. baseline) and any variations that might come due to participants starting at different levels of tiredness.
However, ANCOVA is generally good for comparison between groups. I only have one group and everyone is doing the same tasks. I can treat every participant as a group (since I want to compare within participants), and run ANCOVA but I am not convinced this is the right approach.