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Section 1 Part 1

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Samples vs Population Benefits of getting data from the entire population…. You can draw a conclusion about the entire population….more accurate Benefits of sampling… Easier to collect the data Cost effective

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Good Samples A sample chosen by chance avoid bias by giving all individuals an equal chance to be chosen.

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Simple Random Sample (SRS) A simple random sample of size n consists of n individuals from the population chosen in such a way that every set of n individuals has an equal chance of being selected.

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Examples of SRS’ Choosing a name out of a hat or cup Using a computer to randomly select the individuals Use a random digit table to select the individuals.

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Why is it so important to choose a sample Randomly? ___________________________

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How do we randomly choose samples in nature? ________________________________

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Fish in the lake Activity

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Bad Samples What make a sample bad? Not representative of the population Biased towards one portion of the population Too small Loaded questions Inappropriate methods of collecting data

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Example LOADED Questions “Should the President have the line item veto to eliminate waste?” (97% said yes: ) “Should the President have the line item veto?” (57% said yes: )

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Bias The design of a statistical survey is biased if it systematically favors certain outcomes. BIASED SAMPLING METHODS A Voluntary Response Sample chooses itself by responding to a general appeal. Write-in or call-in opinion polls are examples. Ex; Sales feedback at car dealerships Selection of whichever individuals are easiest to reach is called Convenience Sampling. Survey’s in malls

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Example Bad Sampling Methods – Create BIAS 5-Star Ford house in DFW asks their customers before they leave the dealership how they would rate their buying experience. If they would give a rating of 5, then they will be placed on the call list for customer service ratings.

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Homework

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