Total number of tsetse flies caught (N) in the different areas of the FFCI base and the different seasons. 95% confidence interval ), where CI is the confidence interval; N is the sample mean; t is the critical value of the Student distribution corresponding to the confidence level chosen and the degrees of freedom associated with the sample; n − 1 is the degrees of freedom, where n is the sample size; s is the standard deviation of the sample; is the square root of the sample size.