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.
The selection of participants into experimental or control group is completely randomized (akin to tossing the coin) and many times decided by a computer based program. These studies are hence, called as randomized studies. You have a 50:50 chance of being a part of either of the groups.