The data in WAGE2.RAW on working men was used to estimate the following equation:

Where educ is years of schooling, sibs is number of siblings, meduc is mother's years of schooling, and feduc is father's years of schooling.
(i) Does sibs have the expected effect? Explain. Holding meduc and feduc fixed, by how much does sibs have to increase to reduce predicted years of education by one year? (A non-integer answer is acceptable here.)
(ii) Discuss the interpretation of the coefficient on meduc.
(iii) Suppose that Man A has no siblings, and his mother and father each have 12 years of education. Man B has no siblings, and his mother and father each have 16 years of education. What is the predicted difference in years of education between B and A?

educ 10.36 094 sibs .131 meduc .210 feduc n 722, R 214,