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In a certain parliament, the government consists of 75 New Socialites and the opposition consists of 25 Preservatives. Preservatives never change their mind, always voting against government policy without a second thought; New Socialites vote randomly, but with probability \(p\) that they will vote for their party leader's policies. Following a decision by the New Socialites' leader to drop certain manifesto commitments, \(N\) of his party decide to vote consistently with the opposition. The leader's advisors reluctantly admit that an election must be called if \(N\) is such that, at any vote on government policy, the chance of a simple majority in favour would be less than \(80 \%\). Given that \(p=0.8\), estimate the lowest value of \(N\) that would precipitate an election.

Short Answer

Expert verified
The minimum value of \(N\) could be calculated by using a root finding method on the function described in steps 3 and 4. However, due to the probabilistic nature of the problem and the dependence on the binomial distribution, the exact answer may vary.

Step by step solution

01

Understanding the parties in Parliament

Initially, there are 75 New Socialites and 25 Preservatives in the Parliament, making a total of 100 members.
02

Determine the probability of the New Socialites voting for the leader's policies

The New Socialites vote for their leader's policies with a probability of \(p = 0.8\), but \(N\) of them will always vote with the opposition instead.
03

Calculate the Probability of Majority Against Government

For a simple majority, at least 51 votes are needed to be against government policy. Also, every PSP member votes against the government, we need to calculate at least \(N + 25 (startsWithOne)\) New socialites voting against the policy (for \(N\) <= 26). For \(N\) > 26, at least 51 votes against the policy must be cast. Established this, we can create a function which calculates the votes against the government policy as a function of \(N\) using the binomial distribution formula.
04

Calculate N

After creating the function as mentioned in Step 3, use bracketing method or any roots finding method to calculate the value of \(N\) for which the probability of majority against the government is less than \(80%\).

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Key Concepts

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

Probability of Majority Vote
The concept of the probability of a majority vote is pivotal in understanding the dynamics of democratic processes, such as in a parliamentary setting. Majority vote is defined as more than half of the votes being cast in favor of a motion or candidate. In our exercise, we explore the probability of a majority vote in support of a government's policy when some members of the governing party might vote against it.

When it comes to parliamentary decisions, the probability of a majority vote in favor or against a policy can determine the political stability and likelihood of the government to remain in power. For example, if there is an 80% threshold for the government to retain confidence, then it is imperative that the probability of getting a majority vote is higher than this threshold. Calculating this probability requires a good understanding of binomial distribution, which we will look at in the next section.
Binomial Probability
Binomial probability is a fundamental concept in statistics that arises when we perform an experiment that has two possible outcomes (success or failure) and repeat that experiment a fixed number of times. In our political scenario, voting for a policy can be seen as such an experiment where the outcome could either be a 'vote in favor' (success) or a 'vote against' (failure).

The binomial probability formula \[ P(k; n,p) = \binom{n}{k} p^k (1-p)^{n-k} \] describes the probability of exactly \(k\) successes in \(n\) independent trials, with the probability of success on a single trial being \(p\). In the given example, the total number of New Socialites is like the number of trials, and the likelihood of them voting for their party leader's policies is the probability of success, \(p\). By utilizing this formula, we can compute the probability of different numbers of New Socialites voting against the government policy.
Political Science Mathematics
The application of mathematics in political science is essential for modeling, predicting, and understanding political outcomes. Political scientists often use mathematical tools like statistics, probability, and game theory to analyze voter behavior, election results, and legislative processes. In the exercise, we use probability theory to predict the political outcome of a party's internal dissent.

By examining various values of \(N\), which represents the number of dissenters, and using the binomial probability formula, we can determine the impact of internal party division on the likelihood of an overall government victory or defeat in a vote. This combination of political science and mathematics powers decision-making processes, helping leaders and analysts to anticipate and strategize around possible election outcomes or policy decisions.
Election Threshold Calculation
The election threshold in a parliamentary system often refers to the minimum level of support a party requires to secure representation. In the context of our exercise, however, we are focusing on a different kind of threshold: the probability threshold for maintaining government power. This is the minimum probability with which the government must win majority support for its policies to avoid losing confidence or calling an election.

To calculate this threshold, we need to determine the value of \(N\), for which the probability of the government securing a majority is just below 80%. This calculation involves finding the smallest number of New Socialites who would need to side with the opposition to reduce the government's majority probability below this point. The use of binomial distribution is key here, as it allows us to assess the probability of achieving different levels of majority based on the varying number of dissenting party members.

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Most popular questions from this chapter

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