In this tutorial, we learn how to know the difference: census, study, & sample survey. The census is when everyone's opinion is needed. An example is when you will see census studies happen throughout the year from the government seeing how many people live in one household. A study is when you only need the opinion of experts. This can be when companies are releasing a new product and need the opinions of doctors or dentists about it. A sample survey is when a few people's opinions are enough. This is just a sample of other people and doesn't represent everyone else.