Parameters & Statistics (College Board AP® Statistics)
Study Guide
Written by: Naomi C
Reviewed by: Dan Finlay
Parameters & statistics
What are parameters?
A population refers to the whole set of things which you are interested in
For example, if a vet wanted to know how long a typical French bulldog slept for in a day, then the population would be the sleeping times of all the French bulldogs in the world
A population parameter is a numerical value which describes a characteristic of the population
For example, if the population is all the heights of 16-year-olds in the US
then the mean height of all 16-year-olds in the US is a population parameter
Population parameters are usually unknown
What are statistics?
A sample statistic (often just called a statistic) is a value computed using data from a sample taken from the population
For example, the mean height of 200 16-year-olds from randomly selected cities in the US is a sample statistic
Sample statistics are frequently used to estimate population parameters
What notation is used to represent parameters and statistics?
The notation used for a particular variable can often indicate if it is a population parameter or a sample statistic
Greek letters are used for population parameters
English letters are used for sample statistics
The sample mean,
is used to estimate the population mean,
The sample standard deviation,
is used to estimate the population standard deviation,
The sample chi-square value,
is used to estimate the population chi-square value,
There is only one exception to the rule in this course:
the sample proportion, , is used to estimate the population proportion,
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