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Lesson 2: Probability models

# Making predictions with probability

Predict the number of times a spinner will land on an elephant. The theoretical probability helps us get close with our prediction, but we can't know for sure until we actually spin the spinner.

## Want to join the conversation?

• I think that probability is more about the chance of what will happen in future events and you try and predict that. Am I right?
• Yes, I believe that you are correct.
• What if the following information is given?
1. Where is the arrow pointing at the starting of the experiment?
2. Approximately how many times does it go through the entire circumference in each roll?
--> Will that affect the probability?
• Yes, where the spinner starts and how many times it goes around the spinner are both factors, but the amount of force you put on it is one of the most important factors that is extremely hard to be intentionally duplicated, so it is very hard to force the spinner to land on a certain triangle.

Here it is all laid out.

Probability = Factor( Starting point, Force, Weight of arrow, ......)
Force = How hard you push or flick or hit the arrow
Force = MPH (Miles per hour) If you flick the arrow extremely hard, it will go faster.
If you start on the monkey and flick it so that it spins three times completely around, and ends up on the elephant next to it, then if you applied the same amount of force to the arrow starting on the mouse next to the monkey, then you know it will land on the monkey.
The problem is, it is very hard to apply the exact amount of force to make the arrow land on a certain triangle over and over.

I hope this helps! Have a great day!
• If you had to choose an answer to this question at random, what is the chance you will be correct?

A)25%
B)50%
C)0%
D)25%
• depends on how many questions there are and how many answers it asks for
• *What grade is this appropriate for?*
• any grade. a super smart kindergartner, a coolege student, really anybody can learn this.
• How do you figure the possibility of getting the elephant all 210 times?
• That's a nice question! For independent events (in this case, every spin is independent, meaning it's not related to the previous spins), the probability of a specific outcome happening across all these events is found by multiplying the probability of the event happening once by itself for the number of events. In other words, you raise the probability of the event happening to the power of the number of events.

To answer your question, in our example the probability of spawning an elephant is 4/7 and the number of spins is 210, then the probability of getting an elephant on all 210 spins is (4/7)^210.

This number is astronomically small and, it's virtually zero. So for all practical purposes you could say it's impossible to spawn 210 elephants in 210 spins.
• I am having difficulty with this problem:
Three coins are tossed simultaneously 250 times. The distribution of various outcomes is listed below :
(i) Three tails : 30,
(ii) Two tails : 70,
(iii) One tail : 90,
(iv) No tail : 60.
Find the respective probability of each event and check that the sum of all probabilities is 1.
• They are asking this: you are told that three coins are being flipped at the same time; what is the probability of each event? The values they give you are actually not necessary, since you know that any coin toss is 50/50.

So toss three coins: they each have a 50% chance of being tails. You can make a tree where the branches split into the possibilities, and then count how many there are. Then the chance for each outcome is how many times it actually happens, divided by the total number of outcomes. All the possible outcomes added together should give you 1, which is also 100%. Try it, and tell me how it goes!

Ps, there are certainly videos on KA about questions like these. If you continue to have trouble, I will find them for you.
• I assume the possibility of getting no elephant in 210 spins is the extremely low (3/7)^210, right?
• When you flip a coin, isn't the possibility of getting all heads the same as getting heads, tails, heads, tails, heads, tails, and so on the same? So, I am saying that isn't getting exactly a one-in-two chance of getting heads the same probability of getting all heads?