As a result of the use of random assignment to treatment, randomized experiments typically have high internal validity. However, units are very rarely randomly selected from a well-defined population of interest into an experiment; this results in low external validity. Under nonrandom sampling, this means that the estimate of the sample average…

Several classroom demonstrations are described that have sparked student involvement in undergraduate courses in probability and statistics. These demonstrations involve experimentation using exams and statistical analysis and adjustment of exam scores. (Author/SLD)

A detailed multisite evaluation of instructional software, the ConStatS package, designed to help students conceptualize introductory probability and statistics, yielded patterns of error on several assessment items. Results from 739 college students demonstrated 10 misconceptions that may be among the most difficult concepts to teach. (SLD)