Ronnie Hinson has penned the lyrics to some of Southern Gospel music's greatest songs. The Lighthouse is one such song that has indeed stood the test of times. It bears testimony to the power of God's Holy Spirit and His Word to lead wayward souls to the safe harbor of Christ's Grace.
The average absolute deviation (or mean absolute deviation) of a data set is the average of the absolute deviations from a central point. It is a summary statistic of statistical dispersion or variability.
Both standard deviation and mean deviation are measures of variation (spread from a central value like mean) in data. It is the mean/average of absolute deviations of data point from mean as suggested by name i.e. we subtract the mean from each data point; take it's absolute value (non-negative); sum it up and divide by the number of observations.