Imagine you’re cooking a giant pot of soup for a crowd. You don’t need to eat the whole pot to know if it’s salty enough—you just stir it well and taste a spoonful. That spoonful is your sample. In marketing research, we face the same question: how many spoonfuls (survey respondents) do we need to trust that the whole pot (our target population) really tastes a certain way? This chapter gives you the tools to decide, balancing accuracy with time and money.