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.
Permuted blocks is a method of randomization that randomly assigns individuals to a treatment method. In the case of permuted blocks the assignments are based on both a block (method) and a ratio of allocation to the blocks (1:1 this case). Here's a blurb from wiki on permuted block randomization. Quote: