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The juror pool for the upcoming murder trial of a celebrity actor contains the names of 100,000 individuals in the population who may be called for jury duty. The proportion of the available jurors on the population list who are Hispanic is 0.40 . A jury of size 12 is selected at random from the population list of available jurors. Let \(X=\) the number of Hispanics selected to be jurors for this jury. a. Is it reasonable to assume that \(X\) has a binomial distribution? If so, identify the values of \(n\) and \(p\). If not, explain why not. b. Find the probability that no Hispanic is selected. c. If no Hispanic is selected out of a sample of size 12 , does this cast doubt on whether the sampling was truly random? Explain.

Short Answer

Expert verified
It's reasonable to assume \(X\) follows a binomial distribution with \(n = 12\) and \(p = 0.40\). The probability of selecting no Hispanics is \(0.0022\), suggesting non-randomness if no Hispanics were indeed chosen.

Step by step solution

01

Check the Binomial Conditions

To determine if \(X\) follows a binomial distribution, check for: 1) a fixed number of trials \(n\), 2) each trial is independent, 3) two possible outcomes (Hispanic or not), and 4) the probability \(p\) of a Hispanic being selected is constant. Here, \(n = 12\), and \(p = 0.40\), which satisfies the binomial conditions given a large population size (100,000) ensuring independence.
02

Define Binomial Distribution Parameters

Since the conditions for a binomial distribution are satisfied, identify \(n = 12\) as the number of trials and \(p = 0.40\) as the probability of a trial resulting in 'Hispanic.' Thus, \(X\) is binomially distributed, \(X \sim B(n = 12, p = 0.40)\).
03

Calculate the Probability of No Hispanic Jurors

The probability that no Hispanic is selected \((X = 0)\) in a binomial distribution is found using \(P(X = 0) = \binom{n}{0} p^0 (1-p)^{n}\). Compute this as follows: \[P(X = 0) = \binom{12}{0} (0.40)^0 (0.60)^{12} = (0.60)^{12} \approx 0.0022.\]
04

Interpret the Probability

Given \(P(X = 0) \approx 0.0022\), which is a very low probability, this indicates that it is highly unlikely to select no Hispanics at random from the pool, assuming the sampling was random.
05

Assess Randomness Based on Probability

The low probability of \(0.0022\) for selecting no Hispanic jurors suggests that it is improbable in a truly random sample, thus casting doubt on the randomness of the selection process if indeed no Hispanics are chosen.

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Key Concepts

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

Probability Calculation
In probability theory, calculating probabilities involves understanding the likelihood of various outcomes. For a problem involving a binomial distribution, such as selecting jurors, it's important to know that there are clear criteria that make a situation suitable for using a binomial model. The binomial distribution describes the number of successes in a fixed number of independent trials, with each trial having two possible outcomes and a constant probability of success. In the jury selection exercise, when calculating the probability that no Hispanics are selected as jurors, we use the binomial formula:\[ P(X = k) = \binom{n}{k} p^k (1-p)^{n-k} \]Here, \(n = 12\), which is the total number of jurors, and the probability \(p = 0.40\) for selecting a Hispanic juror, thus \(1-p = 0.60\). For zero Hispanic jurors (\(k=0\)):\[ P(X = 0) = \binom{12}{0} (0.40)^0 (0.60)^{12} \]Simplifying this calculation, we get \((0.60)^{12} \approx 0.0022\). This probability of approximately 0.0022 indicates a very low chance of this event happening if the process is truly random.
Random Sampling
Random sampling is a technique where each member of a population has an equal chance of being selected. This ensures that the sample is representative of the entire population, which is crucial in various fields, including statistics, to avoid bias and ensure valid conclusions. In the context of jury selection, the available pool of 100,000 individuals represents the population from which a random sample of 12 jurors is drawn. Random sampling works under the assumption that the selection process allows each person an equal chance of being picked, with the goal of minimizing bias. This is particularly important in legal settings where the diversity and fairness of a jury can significantly impact the outcome of a trial. If, by chance, no individuals from a particular demographic group are selected, it questions the randomness of the process. In our problem with a small probability of selecting no Hispanic jurors, it naturally leads one to reassess whether the selection was genuinely random or if there was an unforeseen bias.
Jury Selection
Jury selection is a critical component of the legal system, aiming to ensure a fair trial by constituting a jury that reflects the community's diversity. The selection process often begins with a pool of eligible individuals, who are randomly called for potential jury duty. The approach should ideally be representative of community demographics, allowing for a balanced and impartial jury.The binomial distribution provides a useful model for understanding how likely it is that different demographic groups will be chosen from the pool. This is especially important when considering the probability of certain outcomes, such as no members of a particular ethnic group being selected. In this exercise, the concern arises when the probability of not selecting any Hispanic jurors is calculated as very low (\(0.0022\)), potentially questioning the randomness and fairness of the selection process. It suggests that, in real-world scenarios, deviations from expected probabilities could warrant further investigation to ensure fairness and unbiased selection.

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Most popular questions from this chapter

A random number generator is used to generate a real number between 0 and 1 , equally likely to fall anywhere in this interval of values. (For instance, \(0.3794259832 \ldots\) is a possible outcome.) a. Sketch a curve of the probability distribution of this random variable, which is the continuous version of the uniform distribution (see Exercise 6.1). b. What is the mean of this probability distribution? c. Find the probability that this random variable falls between 0.25 and 0.75 .

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