Here is the question: An experiment has developed an "excitability score" for rats as a composite of a number of behavior indices. The experimenter is looking for evidence of association between the excitability score and the strain the rat belongs to. Some 25 rats are selected at random from each of the four pure strains, giving a total of 100 individuals in all. Within each strain used in the experiment, a grouped frequency distribution of "excitability scores" is found, the same class intervals being used for each distribution. Test the hypothesis that all four strains have the same distribution, on the basis of the data (image).
I'm having trouble understanding how to solve this problem, especially since there is no Expected table (or observed table). I tried calculating one but got incorrect values. What should I do? I wasn't sure if i was supposed to make chi square tests between strain 1 and strain 2, then strain 2 and strain 3, etc. I'd appreciate any advice, thanks!