When is it useful to use dot maps and choropleth maps?

Question

Choropleth maps- map in which ranked classes of some variable are depicted with shading patterns or colors for predefined zones.
Dot maps- map which uses a dot to represent the occurrence of some frequency of the mapped variable.

Answer 1

Choropleth maps are one of the simplest methods of representing data that have been collected for areal units. They are commonly used to map census demographic data based on townships or census divisions. To produce a choropleth map, we simply group the observations into a set of classes based on their data values and then shade each class with an appropriate colour of shading pattern. If we are working with nominal scale data, we would choose ungraded patterns or colours, i.e. patterns or colours having equal visual weight, since we are only interested in being able to distinguish between different classes. If we have ordinal, interval or ratio scale data, then we should use graded series of colours or patterns. For example, we might use different shades of one colour ranging from a very pastel shade for the smallest data values to a darker shade for the highest data values. If a larger number of classes are required, we could use shades of two colours to show classes that are above or below average.

An important consideration in producing a choropleth map is the choice of classification scheme to be used. With nominal and ordinal scale data, we generally are given a set of classes. However, with interval and ratio scale data, we must first group the observations into classes. The classification scheme that we choose can have a major impact on the visual impression created by the map. Ideally, we want to classify the data in a way that reveals whatever spatial variation exists within our study area and that minimizes the potential for misinterpretation of the map. We also need to consider whether we are interested in a single map or want to compare a series of maps. In the latter case, we must choose our classes systematically to ensure that the maps are comparable.

Several classification methods have commonly been used in producing choropleth maps. Usually a classification scheme is selected after examining the range and distribution of data values.

I think i said enough about dot maps on your previous question. Good luck man

Answer 2

To allow the presentation of data , graphically when more than one variable needs to be demonstrated.

Answer 3

Amazed that I found this question already answered! it's like you've read my mind!