The specification of a zone within a population, based on a sample mean and its standard error, within which the true mean most probably lies is called?

The correct answer is confidence interval. A confidence interval is a statistical range derived from sample data that is likely to contain the true population mean with a certain level of confidence, usually expressed in percentages such as 95% or 99%. It accounts for the variability within the sample and provides an estimate of how much the sample mean might deviate from the actual population mean.

The confidence interval is calculated using the sample mean plus and minus a margin of error, which is typically determined by the standard error and a critical value from the normal distribution (or t-distribution, depending on the sample size and whether the population standard deviation is known). This specification helps researchers and statisticians make informed inferences about the population from which the sample was drawn.

The other terms provided do not describe the specific concept of a range that estimates the true population mean as effectively as "confidence interval." A confidence zone is not a standard term in statistics, a probability zone does not specifically refer to the estimation of population parameters, and the coefficient of determination is a statistical measure that indicates the proportion of variance for a dependent variable that's explained by an independent variable in a regression model.