The most common and efficient way to find z/2 for a given confidence range is to use a Z-table. The correct option is A.
When constructing a confidence interval, you often use the standard normal distribution (z-distribution) and its critical values. A confidence interval is a statistical tool used to estimate the range in which a population parameter, such as the mean or proportion, is likely to fall. It provides a range of values within which we can be reasonably confident that the true parameter value lies. The level of confidence is expressed as a percentage, and a common choice is 95%.
Therefore, the most common and efficient way to find z/2 for a given confidence range is to use a Z-table. It's readily available, easy to use, and provides the necessary critical z-value for constructing accurate confidence intervals.