A Texas manufacturer of concrete pipe and other precast concrete products for highways, farms, and commercial construction wanted to project sales for improve production planning and logistics operations. It was considered that many variables affected sales, such as: time, population, beginnings of urbanization, construction employment, number of residential units, highway budget projections, number of farms, structure building permits businesses and number of competing companies in the state. A regression analysis multiple showed three key variables for the projection of sales: population, employment on construction and building permits from the previous year. to.

Do you think there is a cause and effect relationship between these variables and sales of the company?

b. Are there other important variables that should be considered that were not on the original list?