Our first method of analysis was to show trends and fluctuations of murder in the city of Austin over a fifteen year time span.
Variables change through time and are measured using trends.
Three types of components are possible when showing these trends. They include secular trends, cyclic variations and random variations. Moving averages are used to reduce irregular fluctuations in trends. They are calculated by finding the averages for successive and overlapping groups of three or five years. A three year moving average was calculated for murder rates in the city of Austin from the period of 1980 to 1994.