In Problem 19 in Chapter 5 and Problem 14 in Chapter 8, data from the 1990 Census for 26 randomly selected Metropolitan Statistical Areas (MSAs) were discussed. Of interest were factors potentially associated with the rate of owner occupancy of housing units. The following three variables were included in the data set:
OWNEROCC: Proportion of housing units that are owner-occupied (as opposed to renter occupied)
OWNCOST: Median selected monthly ownership costs, in $
URBAN: Proportion of population living in urban areas
It is also of interest to see whether the owner occupancy rate-ownership cost relationship is different in metropolitan areas where 75% or more of the population lives in urban areas compared to metropolitan areas where less than 75% of the population lives in urban areas. For this purpose, the following additional variable is defined:

a. State a single regression model that defines straight-line models relating OWN-EROCC to OWNCOST both for MSAs with high percentages (≥ 75%) of urban populations and for MSAs with lower percentages of urban populations (≥ 75%).
b. Using the computer output given next, test whether the straight lines for the two MSA types described in part (a) coincide.
c. Test H0: "The lines are parallel" versus HA: "The lines are not parallel."
d. In light of your answers to parts (b) and (c), comment on differences and similarities in the owner occupancy rate-ownership cost relationship for the two types of MSA.
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