With iodide, the solvate $\ce{NaI \cdot 3(CH3)2CO}$ can be formed, in which each $\ce{Na+}$ is coordinated by 6 acetone ligands via oxygen lone pairs, and the $\ce{I-}$ ions fill in the gaps between these octahedral units, being surrounded by the methyl groups of the acetones.
Randomization is a sampling method used in scientific experiments. It is commonly used in randomized controlled trials in experimental research.
Confounding Variable A goal of conducting a randomized experiment is to make a causal conclusion about the effect of an independent variable on a dependent variable. In order to make a causal conclusion, one must be able to rule out all other explanations for the effect on the dependent variable.