Solution :
a). There is a way to state the question :
If there are two firms, firm A and firm B. Both the forms are same in all the respects but differ in only one thing, that firm A provides job training 1 hour per worker more than the number of hours of training of firm B, by how much the output of firm A would differ than the output from firm B?
b). The manufacturing firms that are located in Ohio will provide the job training based on the characteristics of workers. Some of the determining factors includes years of schooling, experience in a particular job, etc. The firms can even consider the worker's age, race or gender. The training will be provided to the less efficient workers based on their ability.
c). The amount of the capital as well as the technology that is available to the workers would affect the output of the firm. Thus the firms having the same kind of employees would have different outputs when the firms used different technology or different amount of capital.
d). No, unless the training is randomly assigned. The factors are listed above which can contribute to the finding of a positive correlation between the output and the training even when the job training does not improve the productivity of the worker.