Answer & explanation:
A confidence interval is an estimated range of a parameter of interest. Confidence intervals are used to indicate the reliability of an estimate. For example, a confidence interval can be used to describe how reliable a search result is.
In other words, a high confidence interval Z value implies that a survey is more likely to indicate the actual values being presented.
In biostatistics, for example, the Z value can be used in calculations to assess the prevalence of a particular disease and the factors associated with it in a population.
The value of Z, however, is not used as a percentage (like the 99.5% addressed in this question) for calculations. A universal table is used to convert Z values and use them in statistical calculations.
Some examples of Z value conversions can be found in the table attached in this question.
