As described in Statistics Defined, a sample is a set of raw data values drawn from a much larger source, the population. Purpose is …. Before drawing a sample, an investigator should clearly define the population from which it is to come. Outline of this essay …

In order for a sample to be effective in achieving its purpose, its selection must have the property of randomness ….

- Random sample

Simple (SRS) is one in which every possible sample of the desired size has an equal chance of being selected …

- Explain in simple terms why a given sampling method may be unsatisfactory
- A sample is biased if in some critical way it does not represent the population
- Sample statistics
- Location
- Mean
- Median, ;

- Spread
- Standard deviation

- Recognize that the sample mean, , can be regarded as a random variable
- In general, any statistic, G
_{s}, computed from a random sample is a random variable and has an associated sampling distribution - Sampling error
- Is not a mistake, but rather refers to the natural variability between samples
- Relates to confidence of statistical claims

- Location

- Standard error,

- Sampling distribution
- The probability distribution showing how a sample statistic, G
_{s}, varies - Unbiased if its mean is equal to the associated population parameter

- The probability distribution showing how a sample statistic, G

A sample is the result of n (chance) experiments in which the same quantity is measured ….

Sample size, n