Probability - By Anywhere Math
Transcript
| 00:0-1 | Welcome to anywhere Math . I'm Jeff , Jacobson and | |
| 00:02 | today we're talking about probability . Yeah . Today we're | |
| 00:26 | gonna learn about probabilities . Now before we learn how | |
| 00:29 | to find probabilities , let's talk about exactly what probabilities | |
| 00:32 | are . Well , probability is just a number and | |
| 00:37 | you can write that number as a fraction decimal or | |
| 00:40 | percent . That measures the likelihood that an event will | |
| 00:44 | occur . Okay now probabilities will range all the way | |
| 00:50 | from zero up to one . Uh right in the | |
| 00:57 | middle would be one half . Remember we can write | |
| 01:01 | probabilities as a fraction decimal or percent . So I | |
| 01:05 | can also think of this as 0.5 or 50% . | |
| 01:09 | Here will definitely be one as a percent . It | |
| 01:13 | would be 100% . And at the other end zero | |
| 01:17 | or 0% . Okay now in the definition it said | |
| 01:22 | probability is a measure of the likelihood an event will | |
| 01:26 | occur . Now what that means is well if something | |
| 01:30 | has a probability of one or 100% that means it | |
| 01:35 | is certain to happen . Okay , Today my time | |
| 01:41 | is monday . I don't know about you when you're | |
| 01:43 | watching this video but today for me is monday . | |
| 01:46 | The probability for me that tomorrow is Tuesday is 100% | |
| 01:51 | or one . It's certain I'm certain tomorrow is going | |
| 01:55 | to be Tuesday . Okay . Um on the other | |
| 01:59 | hand , down here zero , the probability if something | |
| 02:03 | is zero , we call that impossible . Okay . | |
| 02:10 | You may have heard people use uh the expression when | |
| 02:14 | pigs fly right ? If someone wants you to do | |
| 02:17 | something you said ? Yeah . Yeah sure . When | |
| 02:18 | pigs fly , well that's they say that because it's | |
| 02:21 | impossible right , pigs are never gonna fly unless you | |
| 02:24 | have some weird contraption . You put them in an | |
| 02:26 | airplane . But the point is probability . If it's | |
| 02:29 | zero , well that's impossible . It's never gonna happen | |
| 02:33 | . Um Then a probability of one half . Well | |
| 02:37 | that's kind of right on the edge . If we're | |
| 02:40 | flipping a coin , what's the probability of getting heads | |
| 02:44 | ? Well it's a half because there's only two sides | |
| 02:47 | we would say you're just as likely to flip heads | |
| 02:51 | as you are to flip tales . So a probability | |
| 02:55 | of one half we say that is as likely as | |
| 03:01 | not . Again you're just as likely for that thing | |
| 03:06 | to happen as not happen . Right . 50 50 | |
| 03:10 | 50% chance now , what about anywhere in here ? | |
| 03:15 | Well anywhere between one half and one . The probability | |
| 03:19 | of that we would say that likely . Yeah . | |
| 03:24 | Okay now there's varying degrees of how likely it is | |
| 03:29 | . Obviously if you've got something right around here like | |
| 03:32 | 52% let's just barely likely . Right . You're pretty | |
| 03:36 | close to kind of uh you know a 50 50 | |
| 03:39 | shot . Um Whereas all the way up here you're | |
| 03:42 | getting pretty close to certainty . Um This area we | |
| 03:47 | call likely . which means this down here is unlikely | |
| 03:55 | if you've got a probability that's less than a half | |
| 03:59 | or less than 50% . It's unlikely that thing will | |
| 04:02 | happen now . The degrees of how unlikely it is | |
| 04:05 | depends on , you know , where it falls in | |
| 04:08 | this range , something that's only maybe 49% . We | |
| 04:12 | have barely unlikely . It's it's still pretty close to | |
| 04:15 | us likely or not . And again , somewhere down | |
| 04:18 | here that's pretty close to impossible . You know , | |
| 04:20 | winning the lottery . It's not impossible . It's just | |
| 04:24 | very , very unlikely right somewhere way down here . | |
| 04:29 | Um So this is where the range of probabilities will | |
| 04:33 | fall somewhere in here . Okay , let's look at | |
| 04:36 | an example . Alright , example one , there's an | |
| 04:39 | 80% chance of thunderstorms tomorrow describe the likelihood of the | |
| 04:44 | event . So when we're talking about likelihood , we | |
| 04:47 | want a word , okay , we're not looking for | |
| 04:49 | a number of refraction . We already have that . | |
| 04:52 | Right ? We know the probabilities 80% . Well , | |
| 04:55 | 80% . If you remember on that little uh kind | |
| 04:59 | of number line . Well that was in the likely | |
| 05:03 | section . It's not certain . Right ? It's not | |
| 05:06 | 100% . Is not certain . It's not as likely | |
| 05:08 | as not . It's greater than 50% . So it | |
| 05:11 | falls in the likely . So the likelihood of the | |
| 05:14 | event it is likely . Okay , here's some to | |
| 05:21 | try on your own . Alright , example to you | |
| 05:30 | roll a die , what is the probability of rolling | |
| 05:33 | an odd number ? So first let's find a little | |
| 05:36 | formula for probabilities . Now if every outcome is equally | |
| 05:41 | likely . Right ? So for example flipping a coin | |
| 05:46 | , I'm just as likely to get heads as I | |
| 05:48 | am tales rolling a die . All the sides are | |
| 05:53 | equally likely to happen right ? One side is not | |
| 05:55 | bigger or weighted differently . As long as it's not | |
| 05:58 | a trick die . Um So each one has an | |
| 06:00 | equal chance of happening . So if that's the case | |
| 06:03 | , the formula . Well , first probability for short | |
| 06:07 | , we just say P p of the event , | |
| 06:10 | whatever the event is . Okay , we put that | |
| 06:14 | in brackets here or in parentheses here , probability of | |
| 06:17 | the event is equal to the number of favorable outcomes | |
| 06:26 | over the total possible outcomes . That's how you find | |
| 06:40 | probability . Okay , so for example , uh example | |
| 06:45 | to your roll a die . What's the probability of | |
| 06:47 | rolling an odd number ? So I would write it | |
| 06:50 | like this . Well , probability of I want an | |
| 06:53 | odd number . That's the event is . Well , | |
| 06:58 | how many favorable outcomes are there ? How many ways | |
| 07:02 | can I roll an odd number ? Well , I | |
| 07:04 | could roll a one that's odd . I could roll | |
| 07:07 | a three or five . So there are three ways | |
| 07:12 | a 13 or five . There's three ways to roll | |
| 07:14 | an odd number out of the total possible outcomes . | |
| 07:17 | Well there's six sides that I die so there are | |
| 07:20 | six possible outcomes . So my probability is three out | |
| 07:23 | of six . But we always simplify . So I'm | |
| 07:26 | gonna write that as one half . And again I | |
| 07:31 | could write that as 50% if I wanted to or | |
| 07:33 | 0.5 . So that is the probability of rolling an | |
| 07:37 | odd number . Here's some to try on your own | |
| 07:46 | . Thanks so much for watching and if you like | |
| 07:48 | this video please subscribe . |
Summarizer
DESCRIPTION:
OVERVIEW:
Probability is a free educational video by Anywhere Math.
This page not only allows students and teachers view Probability videos but also find engaging Sample Questions, Apps, Pins, Worksheets, Books related to the following topics.
GRADES:
STANDARDS:
