You are asked to study the relationship between hours spent on employee training (measured in hours per worker per week) in a manufacturing plant and the productivity of its workers (output per worker per hour). Describe:

a. an ideal randomized controlled experiment to measure this causal effect:

b. an observational cross-sectional data set with which you could study This effect;

c. an observational time series data set for studying this effect: and

d. an observational panel data set for studying this effect.