The oral questionnaire on family budgets should be in simple form. So the imperfection in the form and the uncertainty in the hearing are apt to be made. As one of the revising methods, I use the cash inspection. This is based upon inspecting whether or not the accounting balance agrees with the savings. This is one of the self-inspection-systems of the survey. But this method can inspect only cash and not goods ; if we make the same mistakes in the sums of the incomes and the expenses, we cannot find the error.
Therefore, this method cannot be taken to be the perfect inspection method. But this deficiency can be compensated by the skill of the survey and the system of the oral questionnaire.