Editor’s Note: After publication of this story, Virginia began to provide separate viral and antibody test data. Meanwhile, three other states and the CDC seem to be mixing their COVID-19 test types.

How many people have the coronavirus in the United States? More than two months into the country’s outbreak, this remains the most important question for its people, schools, hospitals, and businesses ...

This is a preview. Log in through your library . Abstract For two-period crossover trials where the residual carryover can only exist in the presence of treatment effect, Willan (1988, Biometrics 44, ...