The calculation of confidence interval is related to statistics. To calculate it, you need to the values for mean, standard deviation and sample size. These parameters are incorporated to determine the confidence interval. In terms of definition, it is a value range extracted from a data sample. Further understanding can be attained through an example.
Consider that a carpenter is measuring the average weight of 10 wooden sticks. In this case, the sample size would be ten. In addition to that, the range of weights for these sticks is from 6 to 7 kilos and the average is 6.56 kilos. The carpenter is 88% sure that the average weight is 6.56 kilos. In other words, it can be said that the confidence level is 88%.