/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 44 A balanced die with six sides is... [FREE SOLUTION] | 91Ó°ÊÓ

91Ó°ÊÓ

A balanced die with six sides is rolled 60 times. a. For the binomial distribution of \(X=\) number of \(6 \mathrm{~s}\), what is \(n\) and what is \(p ?\) b. Find the mean and the standard deviation of the distribution of \(X\). Interpret. c. If you observe \(x=0,\) would you be skeptical that the die is balanced? Explain why, based on the mean and standard deviation of \(X\). d. Show that the probability that \(x=0\) is 0.0000177 .

Short Answer

Expert verified
a. \( n = 60, p = \frac{1}{6} \). b. Mean = 10, SD \( \approx 3.651 \). c. Yes, \( x=0 \) is significantly less than expected. d. Probability \( x=0 \) is approximately 0.0000177.

Step by step solution

01

Identify Parameters n and p

When modeling the number of 6s rolled with a six-sided die, this is a binomial distribution problem. A binomial distribution is described by two parameters: \( n \), which is the number of trials, and \( p \), which is the probability of success on a single trial. Here, rolling the die 60 times makes \( n = 60 \). The probability of success \( p \), which is rolling a 6 on one trial, is \( \frac{1}{6} \). Thus, \( n = 60 \) and \( p = \frac{1}{6} \).
02

Calculate Mean and Standard Deviation

The mean of a binomial distribution is given by \( \mu = n \cdot p \). Substituting the values we have, \( \mu = 60 \cdot \frac{1}{6} = 10 \). The standard deviation \( \sigma \) is given by \( \sigma = \sqrt{n \cdot p \cdot (1-p)} \). So, \( \sigma = \sqrt{60 \cdot \frac{1}{6} \cdot \left( 1 - \frac{1}{6} \right)} = \sqrt{60 \cdot \frac{1}{6} \cdot \frac{5}{6}} \approx 3.651 \). The mean of 10 indicates that we expect to roll a 6 about 10 times in 60 trials, with a variation typically around \(3.651\).
03

Evaluate the Skepticism for x=0

Given the computed mean of 10 and standard deviation of approximately 3.651, observing \( x = 0 \) sixes is quite far from the expected number of 10 sixes. This discrepancy of more than 2 standard deviations from the mean suggests an unusual event, which might lead to skepticism about the fairness of the die.
04

Calculate Probability for x=0

The probability for \( x = 0 \) successes in a binomial distribution is given by the probability mass function: \( P(X = k) = \binom{n}{k} p^k (1-p)^{n-k} \). For \( x = 0 \), this becomes \( P(X = 0) = \binom{60}{0} \left( \frac{1}{6} \right)^0 \left( \frac{5}{6} \right)^{60} = 1 \times 1 \times \left( \frac{5}{6} \right)^{60} \). Calculating this gives approximately 0.0000177, confirming the provided probability value.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Mean and Standard Deviation in Binomial Distribution
In the context of a binomial distribution, the mean and standard deviation are pivotal in understanding the distribution's behavior. Here, you're rolling a six-sided die 60 times, seeking to count how often a 6 appears.
The mean of a binomial distribution can be found using the formula \( \mu = n \cdot p \). For this scenario, where \( n = 60 \) and the probability of rolling a 6, \( p \), is \( \frac{1}{6} \), the mean becomes \( \mu = 60 \times \frac{1}{6} = 10 \). This tells us that, on average, we should expect a '6' to appear about 10 times over 60 rolls.

The standard deviation provides insight into the typical amount of variation from the mean. It is calculated using the formula \( \sigma = \sqrt{n \cdot p \cdot (1-p)} \). For this exercise, \( \sigma \approx \sqrt{60 \cdot \frac{1}{6} \cdot \frac{5}{6}} \approx 3.651 \). This means we can expect most results to deviate from the mean by about 3.651. Such metrics assist significantly in interpreting the results from probabilistic trials and in gauging reliability.
Probability of Event
Understanding the probability of specific outcomes in a binomial distribution is crucial, especially when the result deviates significantly from the expected mean. In the die-rolling exercise, we're interested in realizing how probable it is to roll zero sixes out of 60 tries.
Using the binomial probability formula \( P(X = k) = \binom{n}{k} p^k (1-p)^{n-k} \), where \( n \) is the number of trials, \( p \) is the probability of success for a single trial, and \( k \) is the number of successes we're interested in, we can calculate this probability.
For our specific case of rolling zero sixes, i.e., \( k = 0 \):
  • \( \binom{60}{0} = 1 \)
  • \( \left( \frac{1}{6} \right)^0 = 1 \)
  • \( \left( \frac{5}{6} \right)^{60} \approx 0.0000177 \)
Hence, \( P(X = 0) = 1 \times 1 \times 0.0000177 \), which tells us there's an incredibly small chance of not rolling any sixes in this set of 60 rolls. This result underlines how rare such an event is, given the expectation.
Skepticism in Statistical Analysis
Statistical analysis often involves evaluating whether observed data match the expectations derived from theoretical probabilities. In the six-sided die exercise, seeing zero sixes out of 60 rolls might justifiably cause skepticism.
The mean number of times to roll a '6' is computed to be 10, with a standard deviation of about 3.651. Observing such a deviation, over two standard deviations below the mean, suggests an improbable event:
  • Under normal conditions, most results should fall within one standard deviation of the mean.
  • Rare results, like zero successes, indicate potential anomalies.
These could suggest unfairness or bias in the die.

While statistics cannot provide absolute certainties, such unexpected results can prompt further investigations. For instance, double-checking the die for proper balance or replicating the experiment under controlled conditions to assess consistency.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

The Mental Development Index (MDI) of the Bayley Scales of Infant Development is a standardized measure used in observing infants over time. It is approximately normal with a mean of 100 and a standard deviation of 16 a. What proportion of children has an MDI of (i) at least \(120 ?\) (ii) at least \(80 ?\) b. Find the MDI score that is the 99 th percentile. c. Find the MDI score such that only \(1 \%\) of the population has MDI below it.

Most phones use lithium-ion (Li-ion) batteries. These batteries have a limited number of charge and discharge cycles, usually falling between 300 and \(500 .\) Beyond this lifespan, a battery gradually diminishes below \(50 \%\) of its original capacity. a. Suppose the distribution of the number of charge and discharge cycles was normal. What values for the mean and the standard deviation are most likely to meet the assumption of normality of this variable? b. Based on the mean and the standard deviation calculated in part a, find the 95 th percentile.

For each of the following situations, explain whether the binomial distribution applies for \(X\). a. You are bidding on four items available on eBay. You think that you will win the first bid with probability \(25 \%\) and the second through fourth bids with probability \(30 \%\). Let \(X\) denote the number of winning bids out of the four items you bid on. b. You are bidding on four items available on eBay. Each bid is for \(\$ 70\), and you think there is a \(25 \%\) chance of winning a bid, with bids being independent events. Let \(X\) be the total amount of money you pay for your winning bids.

Selling at the right price An insurance company wants to examine the views of its clients about the prices of three car insurance plans launched last year. It conducts a survey with two sets of plans with different prices and finds that: \- If plan A is sold for \(\$ 150\), plan \(\mathrm{B}\) for \(\$ 250\), and plan \(\mathrm{C}\) for \(\$ 350,\) then \(45 \%\) of the customers would be interested in plan \(\mathrm{A}, 15 \%\) in plan \(\mathrm{B},\) and \(40 \%\) in plan \(\mathrm{C}\). \- If plans \(\mathrm{A}, \mathrm{B},\) and \(\mathrm{C}\) are sold for \(\$ 170, \$ 250\), and \(\$ 310\) respectively, then \(15 \%\) of the customers would be interested in plan \(\mathrm{A}, 40 \%\) in plan \(\mathrm{B},\) and \(45 \%\) in plan \(\mathrm{C}\). a. For the first pricing set, construct the probability distribution of \(X=\) selling price for the sale of a car insurance plan, find its mean, and interpret. b. For the second pricing set, construct the probability distribution of \(X,\) find its mean, and interpret. c. Which pricing set is more profitable to the company? Explain.

Playing the lottery The state of Ohio has several statewide lottery options. One is the Pick 3 game in which you pick one of the 1000 three-digit numbers between 000 and 999\. The lottery selects a three-digit number at random. With a bet of \(\$ 1,\) you win \(\$ 500\) if your number is selected and nothing (\$0) otherwise. (Many states have a very similar type of lottery.) (Source: Background information from www.ohiolottery.com.) a. With a single \(\$ 1\) bet, what is the probability that you win \(\$ 500 ?\) b. Let \(X\) denote your winnings for a \(\$ 1\) bet, so \(x=\$ 0\) or \(x=\$ 500\). Construct the probability distribution for \(X\). c. Show that the mean of the distribution equals 0.50 , corresponding to an expected return of 50 cents for the dollar paid to play. Interpret the mean. d. In Ohio's Pick 4 lottery, you pick one of the 10,000 fourdigit numbers between 0000 and 9999 and (with a \(\$ 1\) bet) win \(\$ 5000\) if you get it correct. In terms of your expected winnings, with which game are you better off \(-\) playing Pick \(4,\) or playing Pick 3 ? Justify your answer.

See all solutions

Recommended explanations on Math Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.