(Ch 19, stat 1040)

| Term | Definition |
| ---- | ---- |
| Qualitative | A descriptive value (red, blue, high, low) |
| Quantitative | A numerical value (7, 8, 9) |
| Population | The entire set of existing units that investigators wish to study |
| Sample | A portion or subset of the population |
| Parameter | A number that describes a characteristic of a *population* (*10%* of US senators voted for something) |
| Statistic | A number that describes a *sample* characteristic (*71%* of Americans feel that ...) |
> A global consumer survey reported that 6% of US taxpayers used or owned cryptocurrency in 2020. The US government is interested in knowing if this percentage has increased. The University of Chicago surveys 1,004 taxpayers and finds that 13% have used or owned crypto in the past year (2021)

In the above example:
- The *population* was *US taxpayers*
- The *parameter* was *6%*
- The *sample* was *1004 taxpayers*
- The *statistic* was *13%*

## Simple Random Samples
Advantages:
- Procedure is impartial
- Law of Averages
Disadvantages
- Not always possible
- Can be very expensive

## Bias
| Bias Type | Description |
| ---- | ---- |
| Selection | When the procedure that selects the sample is biased |
| Non-Response | Those that don't respond to a survey may have different characteristics than those that do respond |
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