18.X.4 - Examples
Enroll to start learning
You’ve not yet enrolled in this course. Please enroll for free to listen to audio lessons, classroom podcasts and take practice test.
Interactive Audio Lesson
Listen to a student-teacher conversation explaining the topic in a relatable way.
Calculating Probability with Coin Tosses
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Let's look at our first example: Suppose we toss a coin 5 times. We want to find the probability of getting exactly 3 heads. Can anyone tell me how we would set up this kind of problem using the Binomial Distribution?
We would define n as the number of trials, which is 5, right?
Exactly! And what would k represent in this scenario?
K would be 3 since we are looking for 3 heads.
Correct! Now, what about the probability of success, p?
Since we are tossing a fair coin, the probability p would be 0.5 for heads.
Awesome! Now we can plug these values into our Binomial Probability Mass Function. The formula is P(X = k) = (n choose k) * p^k * (1-p)^(n-k). Who can compute the probability?
So, it would be P(X=3) = (5 choose 3) * (0.5)^3 * (0.5)^2 = 10 * 0.125 * 0.25, which equals 0.3125.
Brilliant! So, we find that the probability of getting exactly 3 heads in 5 tosses is 0.3125. Remember the acronym 'NPK' for n, p, k to help you recall the parameters of the Binomial Distribution!
Defect-Free Items in Quality Control
🔒 Unlock Audio Lesson
Sign up and enroll to listen to this audio lesson
Now, let's move on to our second example: A machine produces 80% defect-free items. If we sample 5 items, what is the probability that exactly 4 of them are defect-free?
In this case, n is still 5, and k is 4 since we're looking for 4 defect-free items.
Correct! And what's p for a defect-free item?
That would be 0.8, right? Because the machine has an 80% defect-free rate.
Right again! What’s the probability of failure, q?
Q would be 0.2, since q = 1 - p.
Excellent! Now, let’s compute the probability using the formula. Can someone calculate it for us?
So, P(X=4) = (5 choose 4) * (0.8)^4 * (0.2)^1 = 5 * 0.4096 * 0.2, which gives 0.4096.
Fantastic! So, the probability that exactly 4 items are defect-free is 0.4096. To help remember what we're calculating, think of 'DQ4' for Defect-free Quality in 4.
Introduction & Overview
Read summaries of the section's main ideas at different levels of detail.
Quick Overview
Standard
In this section, we explore two specific examples: the probability of getting exactly 3 heads when tossing a coin 5 times and the probability of having 4 defect-free items from a batch of 5 produced by a machine with an 80% success rate. These examples illustrate the application of the Binomial Distribution formula and its parameters.
Detailed
Detailed Summary
In this section, we delve into practical applications of the Binomial Distribution through two key examples. The first example discusses the probability of getting exactly 3 heads in 5 coin tosses, where each toss has a 50% chance of success (p=0.5). By applying the Binomial Distribution formula, we compute the probability and find that it is 0.3125. The second example involves a quality control scenario where a machine has an 80% defect-free production rate. We calculate the probability of obtaining exactly 4 defect-free items from a batch of 5. The probability in this case is calculated to be 0.4096. These examples not only provide clear illustrations of how to apply the Binomial Distribution formula but also reinforce its relevance in real-world applications.
Youtube Videos
Audio Book
Dive deep into the subject with an immersive audiobook experience.
Example 1: Coin Toss
Chapter 1 of 2
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Example 1:
A coin is tossed 5 times. What is the probability of getting exactly 3 heads?
• Here, n = 5, k = 3, p = 0.5
5
𝑃(𝑋 = 3) = ( )(0.5)3(0.5)2 = 10×0.125×0.25 = 0.3125
3
Detailed Explanation
In this example, we're dealing with a binomial distribution where a coin is tossed 5 times. The objective is to find the probability of getting exactly 3 heads (successes). Here, 'n' (number of trials) is 5, 'k' (number of successes) is 3, and 'p' (probability of getting heads in one toss) is 0.5.
To calculate the probability, we use the Binomial Probability Mass Function (PMF). The formula involves calculating a binomial coefficient which helps in determining the number of ways we can choose 3 success occurrences (heads) out of 5 trials. The intermediate steps yield a probability of approximately 0.3125, meaning there's around a 31.25% chance of getting exactly 3 heads in 5 tosses.
Examples & Analogies
Imagine you're a student flipping a coin 5 times to see how often it lands on heads during your break. You want to know your chances of getting exactly 3 heads. This situation is akin to studying outcomes in a fair game, where you can expect certain results based on probability. If you did this activity repeatedly, sometimes you'd hit the 3 heads mark, and sometimes you'd miss it. The probability calculation shows how often you might expect to see this outcome.
Example 2: Machine Production
Chapter 2 of 2
🔒 Unlock Audio Chapter
Sign up and enroll to access the full audio experience
Chapter Content
Example 2:
A machine produces 80% defect-free items. What is the probability that exactly 4 out of 5 items are defect-free?
• n = 5, k = 4, p = 0.8
5
𝑃(𝑋 = 4) = ( )(0.8)4(0.2)1 = 5 ×0.4096×0.2 = 0.4096
4
Detailed Explanation
In this scenario, we are considering a machine that produces items with a high quality assurance rate, specifically 80% defect-free items. We want to know the probability of selecting 5 items and finding that 4 of them are defect-free. Here, 'n' is again 5, 'k' is 4, and 'p' is 0.8. Using the Binomial PMF similar to the previous example, we calculate the number of ways to achieve 4 defect-free outputs from the 5 items produced, yielding a probability of approximately 0.4096. This translates to around a 40.96% chance that in a sample of 5 items, exactly 4 will be defect-free.
Examples & Analogies
Think of it as a quality control measure in a factory where a new product is being produced with a very high success rate of being flawless. If you're in charge of quality checks and you randomly pick 5 products off the assembly line, you're interested in how likely it is that exactly 4 of these will pass your strict quality tests (be defect-free). This analysis helps you understand the reliability of the production process.
Key Concepts
-
Probability Mass Function (PMF): A formula that gives the probability of specific outcomes in a binomial experiment.
-
Parameters: n (number of trials), k (number of successes), p (probability of success), q (probability of failure).
Examples & Applications
Example 1: Coin Toss - Probability of exactly 3 heads in 5 tosses is calculated as P(X=3) = 10 * (0.5)^3 * (0.5)^2 = 0.3125.
Example 2: Quality Control - Probability of exactly 4 defect-free items from 5 produced with an 80% success rate is P(X=4) = 5 * (0.8)^4 * (0.2)^1 = 0.4096.
Memory Aids
Interactive tools to help you remember key concepts
Rhymes
Heads or tails, if you're in, just add them all together, count your wins!
Stories
Imagine a box of coins, where you toss them to win prizes; 5 tosses decide if you get a treasure or a surprise!
Memory Tools
Remember 'NPK' for the parameters in Binomial Distribution: n trials, p success, k successes.
Acronyms
DQ4
Defect Quality in 4 – to remember the scenario of finding exactly 4 defective items.
Flash Cards
Glossary
- Binomial Distribution
A discrete probability distribution that calculates the probability of exactly k successes in n independent Bernoulli trials.
- Bernoulli Trial
An experiment or process that results in a binary outcome: success or failure.
- Probability Mass Function (PMF)
A function that gives the probability that a discrete random variable is equal to a specific value.
Reference links
Supplementary resources to enhance your learning experience.