Answer to Question 1
How is labor to be measured? Can it be measured in hours, and if not, how can the labor actually used in production be expressed? How are materials to be measured? How are capital assets, which have different rates of depreciation and input intensity, to be measured?
Answer to Question 2
Estimating a production function for a single plant generally uses time-series analysis, because it is possible to know if technology and other variables have remained constant over time. To estimate a production function for a number of firms in an industry, it is customary to use cross-sectional analysis because it is unlikely that technology and other relevant factors have remained constant for all firms in the industry over time, and cross-sectional analysis removes this problem.
The major classes of vertebrates
Major features of the Solar System (not to scale)
Major Motor Pathways
The diaphragm: The major muscle of breathing.
The major internal features of a neuron.
Table - Correlation Analysis