DAT - Example of Data (Lesson)

Example of Data

John Snow

The year was 1854. In the Soho section of London people were becoming ill and dying. It was thought that the disease was airborne, yet there was no proof. Dr. John Snow set out to disprove this myth.

Dr. Snow began mapping the incidences of disease on a map of the district. He used a bar to represent each person that died from the disease which was called cholera. Bars accumulated thickly in some areas and then gradually faded, fading out to the edges of the map. Examining the data, Dr. Snow considered what was at the center of the data and began asking questions, with the most populous areas first.

What was in common?  The data not existing on the edges of the map indicated that the cause was contained in the affected area.  An airborne disease would spread with the wind. Below is the bar graph mapping that Snow did to determine the cause of the outbreak. Dr. Snow irrevocably changed history with this mapping, showing an epidemiological study using data with the right questions could assist in determining answers to questions.

Snow's map helped pinpoint the center, but not the complete problem. Note that the bars are shown at some addresses, but other addresses relatively close have no bars indicating deaths on his map.  He then had to ask the correct questions. Some of the area had eating establishments which had water brought from other locations always. It was a process of deduction and asking the correct questions. Note the pump on Broad Street is the only one with deaths encircling it. Other pumps on the outskirts did not have deaths encircling the pumps. Data can help point to a cause and assist in solutions.

An Updated Present- Day Map

In the image below is present day London with the Snow data overlaid using interactive technology. This is a type of geological heat-map  using color to depict item values located at specific geometric coordinates (x, y) on the graph. The values associated with the circles are either the number of deaths at the location or (-999) indicating a pump for dispensing water.

(a heat map is a geographical representation of data where the individual values contained in a matrix are represented as colors)

An Updated Present- Day Map

View the video below for a modern day, 2014, adaptation of the data into an interactive graphical mapping. 

 

IMAGE SOURCED FROM WIKIMEDIA COMMONS. VIDEO BY GAVS AND USED ACCORDING TO TERMS OF USE.