# AP Statistics Curriculum 2007 EDA Statistics

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## General Advance-Placement (AP) Statistics Curriculum - Statistics

### Definitions

Variables can be summarized using statistics.

• A statistic is a numerical measure (or a function) that describes a characteristic of the sample.
• A parameter is a numerical measure that describes a characteristic of the population.
We use statistics to estimate parameters.

• We use sample-statistics to estimate/understand population parameters or characteristics!

### Example

Suppose we are interested in the meancalory or mean sodium content of hot dogs. It would be difficult to obtain measures of calory and salt content for ALL hot-dogs. However, we can use the Hot dogs datafile that we discussed uearlier. This data contains a sample of 54 major hot dog brands. Some of the interesting population papameters are the mean-calory, mean-sodium, variance-of-calory between hot-dogs and variance-of-sodium between hot-dogs. These measures may be estimated from the sample using the corresponding sample-statistics (sample-averages and sample-variances).

• The histogram of the Calory content of all hotdogs in shown in the image below. Note the clear separation of the calories into 3 distinct sub-populations. Could this be related to the type of meat in the hotdogs?
• The histogram of the Sodium content of all hotdogs in shown in the image below. What patterns in this histogram can you identify? Try to explain!