If we use people as sample cases, then their selection is often because of some prior behavior or characteristic. For example, an observation study might involve product use. We observe a person purchase an item in a store (e.g., box of cake mix) and recruit them for a home-use study. We arrange a time to watch them bake their cake. Do they follow directions precisely or make modifications; what tools (pans, spatulas, bowls) do they use in the preparation of cake batter; what additional products do they use to complete the cake (e.g., fruit preserves or spreads, icing, candies, sprinkles or decorations, candles); do they have difficulties or is the cake a masterpiece? From such a study, we might recommend changes in packaging directions, packaging design, or new products. Sampling design must also answer the following: Who are the contacts to gain access to the sample cases? These are often intermediaries who help with introductions and serve as contacts to reach if conditions change or trouble develops. These intermediaries also provide access to desired records, recording devices, etc.