In mathematics, the term "interval" usually refers to a statistical confidence interval. Confidence intervals describe the likelihood of a statistical estimate being correct. Higher confidence intervals mean better chances that the estimate is correct, while lower confidence intervals mean better chances that the estimate is incorrect or flawed.
To calculate a confidence interval, the researcher needs to have three pieces of information: the confidence level, the statistic and the margin of error. The confidence level is usually given as a percentage (e.g. 90 percent), and the statistic is usually given as a sample mean, while the margin of error is calculated by multiplying critical value by standard deviation or standard error. With this information, the confidence interval can be calculated using a sample statistic plus or minus margin of error.