Aoristic Analysis Example

1 Oct

I have started analyzing crime. The data I get has the time of the crime being the time the report was filed. So, on Monday at 8:00 there are a lot of car burglaries — well, reports of car burglary. When the crime is reported and when it happened are two different things and need to be kept separate. But how does someone who is sleeping know when their car was broken in to?

Digging deeper in to the reports, I can get an estimated start and end time that a crime may have occurred between.  Using Aoristic analysis, I can assign weights to the times to come up with a better understanding of when the highest probability times for certain crimes may be. Here is how it works:

In Excel create a sheet with columns for start and end and then one for each hour of the day 00:00 to 23:00.

For each incident note the start and end time, then count the time between them and mark the value of each hour divided by the total hours.

Start     End          …    1:00   2:00    3:00    4:00    5:00   6:00    …..

2:00    6:00                              .25      .25        .25        .25

3:00    4:00                                            1

1:30     6:30                 .166    .166     .166    .166     .166    .166

SUM                               .166     .416    1.416    .416     .416    .166

The probability is the SUM/Number of incidents (in this case 3)

Each time (1:00) is really 1:00-1:59. So if I crime occurred between 1:00 and 6:00- 1,2,3,4 and 5 are selected, 6 is not.

The highest probability for this type of crime to occur would be at 3:00.  The more data you have the better your results. And use common sense when looking at the results. In my studies, the results have made sense. I have noticed Auto Burglary in the late night and early morning. Home burglary has occurred while people were at work from 9:00 to 4:00.  This makes sense and is shown with the data.

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