  Although the Synthetic Control Method (SCM) is now widely applied, its most
commonly-used inference method, placebo test, is often problematic, especially
when the treatment is not uniquely assigned. This paper discuss the problems
with the placebo test under multivariate treatment case. And, to improve the
power of inferences, I further propose an Andrews-type procedure as it
potentially solve some drawbacks of placebo test. Simulations are conducted to
show the Andrews' test is often valid and powerful, compared with the placebo
test.
