The type II error is the probability of accepting the null hypothesis when it's false.
a. From the information, the proportion of parents who passes the sign language test is not less than 25%.
b. Since the p value is greater than 0.05, the null hypothesis is rejected. Therefore, the proportion of parents who passes the sign language test is not less than 25%.
c. The possible defect in the study is that the parents if the children with hearing problem should be selected randomly.
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