It involves recording the behaviour of shore crabs at regular intervals. The data collected is nominal, as the behaviour is put into distinct catagories (such as 'locomotory activity'/'stationary'/'Aggressive interaction'). The behaviour of two crabs in a tank is scan sampled every 20 seconds for the duration of the 7 day experiment leading to an exact number of samples per crab per per 24 hour period (4320).

The lighting in the tank switches between on and off every 12 hours.

I am attepmting to determine if activity levels and aggression peak at certain times of the day.

So far I have been able to use fishers exact test to detemine a significant difference between activity levels of the 'day' and 'night' phases of the experiment, but analysing differences by hour is not avaliable as Minitab allows for only 2x2 contingency tables.

I cannot use Chi squared test because Minitab returns saying 'Multiple cells have expected values of less than one, Chi squared approximation probably invalid'

Are there any other tests for non-randomly collected nominal data that I should be considering?

...I would also like to divide the total number of aggressive interactions per hour by the of overall activity (locomotory activity + aggressive interactions) per hour to see if aggression increases RELATIVE to overall activity at certain times of the day. (Which would allow to rule out an increase of aggression as a side effect to increased overall activty level).

Would I be able to use the figures in an anova? (All the figures obtained would be bewteen 0 and 1)

E.g

18:00-19:00

Number of aggressinve interactions recorded: 12

Number locomotory activy recorded: 37

12/ (12+37)= 0.244

19:00-20:00

Aggressive interactions recorded: 6

Locomotory activity recorded: 1

6/ (6+1) =0.857

I have 30,240 samples per crab, but not much of an idea how to analyse it. Any help will be much appreciated.