A researcher plans to study the causal effect of the effect of fertilizer application on yield in China, using data from a random sample of villages in China. The researcher plans to regress yields on fertilizer input intensity. 1. Do you think this regression suffers from omitted variable bias? Explain why. Which variables would you add to the regression? (1 point) 2. Using the expression for omitted variable bias, ^1p1+21 assess whether the regression will likely over- or underestimate the effect of fertilizer application on yield. That is, do you think that ^1>1 or ^11 or ^1