Experiments should be designed to facilitate the detection of experimental measurement error. To this end, we advocate the implementation of identical experimental protocols employing diverse experimental modes. We suggest iterative non-parametric estimation techniques for assessing the magnitude of heterogeneous treatment effects across these modes. And we propose incorporating standard measurement strategies in the design that help assess whether any observed heterogeneity reflects experimental measurement error. To illustrate our argument, we conduct, and analyze results from, four identical interactive experiments in the lab; online with subjects from the CESS lab subject pool; online with an online subject pool; and online with MTurk workers.