Several branches of the potential outcome causal inference literature have discussed merits blocking versus complete randomization. Some concluded it can never hurt precision estimates, and some hurt. In this paper, we reconcile these apparently conflicting views, give a more thorough discussion what guarantees no harm, discuss how other aspects blocked design cost, all in terms precision. We d...

Schiff bases exhibited sensor activity via cyclic voltammetry, colorimetry, and UV-vis study at room temperature. The probes could be employed as a low-cost, ultrasensitive chemo-sensor to detect Cu 2+ Zn in solutions.