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### Course: Statistics and probability>Unit 8

Lesson 1: Counting principle and factorial

# Count outcomes using tree diagram

Tree diagrams display all the possible outcomes of an event. Each branch in a tree diagram represents a possible outcome. Tree diagrams can be used to find the number of possible outcomes and calculate the probability of possible outcomes. Created by Sal Khan.

## Want to join the conversation?

• What if all actions aren't equally likely? Does the diagram not work for those, or is there a way for the diagram to represent unequal outcomes?
• You can take the outcome of the product and will be able to see the 8 possibilities so you won't really need the tree
• The tree diagram seems so unnecessary here. You can just take the product of the outcomes and immediately see the 8 possibilities. Is there a more realistic scenario that shows why you would want to use a tree diagram?
• Tree diagrams are best used to facilitate the understanding and visualization of a probility including problem in which the number of equally likely outcomes decreases each time
For example:What is the posibility of choosing 2 red balls individually & consecutively from a bag of 3 blue balls and 2 red balls.?
Answer: first,the possibility of choosing a red ball would be 2/5. Then,since we didn't put the red ball back,the possibilty of choosing another red ball would be 1/4. So, 2/5*1/4 = 2/20 = 1/10
Hope this helped !
• This man explain extremely complicated concepts daily and has made hundreds of videos for years, and yet the hardest part is "changing colors" ?
• who thinks for these concepts?? we dont even use these in REAL life!! but you did great Sal, keep up the good work
• what do you mean REAL life!! ? I use these concepts in REAL life!! and have done for years, now I even use them in my job
• transcript: red, blue, green, white
real life, red, blue, greeeeeeeeeee...eeeen, white
• At Sal ya mixed up the colors again haven't ya? Green doesn't look like green... more like yellowish are ya sure ya didn't mix up the colors.
• I can't seem to understand how is the intuition behind outcome counting related to permutation. Could anyone explain?