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What is a Tree Diagram?

Christine Hudson
Christine Hudson

A tree diagram is an illustration which generally displays all possible outcomes from one root event or how all of its components are related to one another. When thinking in terms of genealogy, a tree diagram would ideally start with one couple, then branch to their children, then on to their grandchildren and so on. In terms of science or mathematics, these diagrams show all possible results which may stem from one compound or event. Even in subjects like history or English, a tree diagram may be used to show how events or ideas connect to one another.

Using a tree diagram in subjects like history may display events and related outcomes in a way in which students understand and remember easier. It is said that 60 percent of the population are visual learners, so diagrams such as these may not only help the individual students, but also aid in overall classroom performance. Other subjects like science and math may use this type of diagram for much the same reason, but diagrams in these subjects tend to show possibilities as well as relationships.

Man climbing a rope
Man climbing a rope

The tree diagram may be used in many industries as well. Companies might create a decision diagram to explore the likely benefits and disadvantages of financial ventures before taking any risk. They can outline future paths to reach certain goals easily as well. Medical professionals sometimes create a tree diagram to explain a certain group’s risk of disease based on lifestyles, genetics, and other factors. Genetic engineers can even use these diagrams to predict the outcomes of different couplings within the plant, animal, and even human kingdoms.

There are even software programs available which create tree diagrams for different purposes. The user may put in a stem occurrence and the number of results he or she wants the program to return. Then the program can quickly analyze the potentialities and build a tree diagram from them. Some programs can even calculate and display the likelihood of each result, such as whether it’s more likely a couple will have a blue-eyed child or a brown-eyed one.

A tree diagram shows how the elements in it are related or how one action or event might end. They are considered a safe way to assess risk and may even be used as a teaching tool. They are most effective when used as a general guideline, as they generally cannot allow for unforeseen variables.

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Discussion Comments


I remember using tree diagrams all the time in high school. Probably the first time we learned them was in mathematics, when they were teaching us about probability.

It's funny how you need that one single lesson, that doesn't seem that important, but it allows you to learn about so many other things later on.

Anyway, I also remember that the teacher taught us about probability by basically making us gamble on what numbers were going to come up when a die was thrown several times.

And then we noted the probabilities into a tree diagram. It took me a long time to really understand this lesson, but I got it in the end.


I actually think a tree diagram in amateur genealogy is better off trying to go the other way.

In the context of historical research, often it will start off with one couple and then show their children and so forth. You might be interested in, say the descendants of a queen or musician.

But, if you are looking for your own ancestors, you'd have to start with yourself at the trunk, then branch off into parents, then sets of grandparents and great grand parents and so forth.

Of course, if you already have children or grandchildren yourself, it could sprout out both ways!

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