Many decisions in healthcare, business, and other policy domains are made without the support of rigorous evidence due to the cost and complexity of performing randomized experiments. Using observational data to answer causal questions is risky: subjects who receive different treatments also differ in other ways that affect outcomes. Many causal inference methods have been developed to mitigate these biases. However, there is no way to know which method might produce the best estimate of a treatment effect in a given study. In analogy to cross-validation, which estimates the prediction error of predictive models applied to a given dataset, we propose synth-validation, a procedure that estimates the estimation error of causal inference methods applied to a given dataset. In synth-validation, we use the observed data to estimate generative distributions with known treatment effects. We apply each causal inference method to datasets sampled from these distributions and compare the effect estimates with the known effects to estimate error. Using simulations, we show that using synth-validation to select a causal inference method for each study lowers the expected estimation error relative to consistently using any single method.

The second annual Robot Competition and Exhibition sponsored by the Association for the Advancement of Artificial Intelligence was held in Washington D.C. on 13-15 July 1993 in conjunction with the Eleventh National Conference on Artificial Intelligence. This article describes the robots that placed first and second in each event and compares their strategies and their resulting successes and difficulties.

Place he 1993 robot competition consisted of the Office, (2) Office Delivery, and (3) Lockheed Palo Alto Research Labs, Second Office Rearrangement. The unifying theme Place for these events was autonomous robotics in realistic office environments. The legs, and then to quickly complete a slalom office contained actual furniture, including course and recognize the finish wall. In the second event, Office Delivery, the This realistic environment was a hurdle for objective was to self-locate using an office conventional robotic sensory systems. Thinlegged map, search an area for a given object (a coffeepot), tables and chairs are nearly invisible to and then navigate to a specified sonars, as are black cabinets and bookcases to delivery area.