# Fundamentals of Statistics

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## 1.6 Sample Selection Methods

Sampling can be done either with or without replacement of the items being selected. Almost all survey sampling is done without replacement.

### Sampling with Replacement

CONCEPT A sampling method in which each selected item is returned to the frame from which it was selected so that it has the same probability of being selected again.

EXAMPLE Selecting items from a fishbowl and returning each item to it after the selection is made.

### Sampling Without Replacement

CONCEPT A sampling method in which each selected item is not returned to the frame from which it was selected. Using this technique, an item can be selected no more than one time.

EXAMPLES Selecting numbers in state lottery games, selecting cards from a deck of cards during games of chance such as blackjack or poker.

INTERPRETATION Sampling without replacement means that an item can be selected no more than one time. You should choose sampling without replacement instead of sampling with replacement because statisticians generally consider the former to produce more desirable samples.