ABSTRACT
Inferential statistics are based on probability. In particular, statistics use a sample to make inferences about a population. To read and evaluate statistics, it is important to understand a few basic principles about how statistics use probability to make these inferences. Two of the most commonly used examples of probability are tossing a coin or rolling a pair of six-sided dice. Confidence levels are expressed as 100% minus alpha. This value refers to the percentage of all possible samples that could include the true population parameter within a suggested range. The range is computed statistically. Confidence levels are typically set at 95%, meaning that the true population number is within the range for 95% of the possible samples that could be drawn from the population. The range of values is called a confidence interval or margin of error, as the media refer to it when reporting the results of public opinion polls.
