What is defined as a listing of observations in a specific order?

An array is a systematic way of organizing a set of observations where each observation is listed in a specific order, typically from the smallest to the largest value or based on another logical arrangement. This ordered listing is crucial for various statistical analyses as it facilitates the understanding of the data's overall structure, including the identification of trends, patterns, or outliers.

In statistics, it's essential to review data in an ordered format for calculating measures of central tendency (like the mean and median) or for understanding the range and dispersion. Organizing data in an array allows for straightforward comparisons and is foundational in many statistical procedures.

The other options, such as parameter, distribution, and grouped data, refer to different statistical concepts. A parameter characterizes a population, a distribution describes how data points are spread across values, and grouped data contains observations organized into classes rather than listed individually or specifically ordered. Hence, an array is the most fitting choice when referring to a listing of observations in a defined sequence.