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Suppose an experiment is done with criminals released from prison in a certain state where the recidivism rate is \(40 \%\); that is, \(40 \%\) of criminals return to prison within three years. One hundred random prisoners are made to attend a "boot camp" for two weeks before their release, and it is hoped that "boot camp" will have a good effect. The null hypothesis is that those attending boot camp have a recidivism rate of \(40 \%, p=0.40\). Report the alternative hypothesis in words and in symbols.

Short Answer

Expert verified
The alternative hypothesis, in words, states that the recidivism rate of criminals who attended the boot camp is less than \(40\% \). Symbolically, this can be expressed as \(H_a: p<0.40\).

Step by step solution

01

Understanding the Null Hypothesis

The null hypothesis, denoted as \(H_0\), is a statement of no effect or no difference and is assumed to be true until statistical evidence indicates otherwise. Here, the null hypothesis \(H_0: p=0.40 \) states that the recidivism rate of criminals attending boot camp is \(40\%\).
02

Formulating the Alternative Hypothesis

The alternative hypothesis, denoted by \(H_a\) or \(H_1\), is what we are testing against the null hypothesis. It assumes there is some effect or difference. Since we hope that the boot camp has a 'good effect', implying a decrease in the recidivism rate, our alternative hypothesis will be that the recidivism rate is less than \(40\%\), which can be symbolized as \(H_a: p<0.40\).

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Key Concepts

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

Recidivism Rate
Recidivism rate refers to the percentage of individuals who relapse into criminal behavior after having served their time in the judicial system. In many criminal justice studies, reducing the rate of recidivism is a significant goal, as it indicates a successful reform and reintegration of former inmates into society. To calculate this rate, one can divide the number of individuals who were rearrested, reconvicted, or returned to prison within a certain period after release by the total number of individuals released. For example, if 40 out of 100 prisoners return to prison within three years, the recidivism rate would be calculated as \( (40/100) \times 100\% = 40\% \).

Understanding the recidivism rate is crucial when evaluating the effectiveness of rehabilitative programs, such as 'boot camps' or other interventions aimed at reducing the likelihood of re-offense. In our exercise, the impact of a 'boot camp' program on released prisoners is investigated with a known recidivism rate serving as a benchmark for success or failure of the program.
Statistical Hypothesis Testing
Statistical hypothesis testing is a method used by statisticians to make inferences about populations based on sample data. This process involves proposing a null hypothesis \(H_0\) and an alternative hypothesis \(H_a\) or \(H_1\). The null hypothesis usually states there is no effect or no difference, and it serves as the starting assumption. The alternative hypothesis posits a specific effect or difference that the researcher expects to observe.

In hypothesis testing, statistical tests are used to determine whether there is enough evidence to reject the null hypothesis. If the data supports rejecting the null hypothesis, the researcher can conclude with a certain confidence level that the alternative hypothesis may be true. In our exercise, a null hypothesis stating the recidivism rate is 40% is tested against an alternative hypothesis suggesting that a 'boot camp' program will reduce that rate below 40%. The goal is to obtain statistical evidence to either support this claim or maintain that the boot camp has no effect.
Boot Camp Effect
The 'boot camp effect' refers to the influence that a short-term, intensive correctional program might have on the behavior of convicted criminals. Boot camps are designed to instill discipline and provide skills that can assist individuals in avoiding recidivism upon release. However, the effectiveness of such programs is often subject to academic and policy debate.

When measuring the boot camp effect on recidivism rate, researchers compare the post-release outcomes of those who completed a boot camp program with those who did not. In the context of our exercise, the hypothesis is that the boot camp will have a 'good effect', presumably leading to a lower recidivism rate than the benchmark state rate of 40%. By conducting such investigations, we can use statistical evidence to determine the impact of boot camps and make informed decisions regarding their implementation and funding in the criminal justice system.

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Most popular questions from this chapter

A professor creates two versions of a 20 -question multiple-choice quiz. Each question has four choices. One student got a score of 19 out of 20 for the version of the test given to the person sitting next to her. The professor thinks the student was copying another exam. The student admits that he hadn't studied for the test, but he says he was simply guessing on each question and just got lucky. For the professor, the null hypothesis is that \(p=0.25\), where \(p\) is the probability that the student chooses the correct answer if just guessing, and the alternative is \(p>0.25\). Would you say that the p-value for this hypothesis test will be high or low? Explain.

Historically, the percentage of U.S. residents who support stricter gun control laws has been \(52 \%\). A recent Gallup Poll of 1011 people showed 495 in favor of stricter gun control laws. Assume the poll was given to a random sample of people. Test the claim that the proportion of those favoring stricter gun control has changed. Perform a hypothesis test, using a significance level of \(0.05\). See page 423 for guidance. Choose one of the following conclusions: i. The percentage is not significantly different from \(52 \%\). (A significant difference is one for which the p-value is less than or equal to \(0.050 .\) ) ii. The percentage is significantly different from \(52 \%\).

A teacher is interested in testing whether offering students some form of incentive improves their GPA. She collects data and performs a hypothesis test to test whether the probability of getting the maximum GPA is greater with an incentive than without. Her null hypothesis is that the probability of getting the maximum GPA is the same with or without an incentive. The alternative is that this probability is greater. She gets a p-value from her hypothesis test of \(0.07 .\) Which of the following is the best interpretation of p-value? i. The p-value is the probability of getting exactly the result obtained, assuming that incentives are effective in this context. ii. The p-value is the probability that incentives are not effective in this context. iii. The p-value is the probability of getting a result as extreme as or more extreme than the one obtained, assuming that incentives are effective in this context. iv. The p-value is the probability of getting a result as extreme as of more extreme than the one obtained, assuming that incentives are not effective in this context. v. The p-value is the probability of getting exactly the result obtained, assuming that incentives are effective in this context.

For a school's annual sports meet, \(56 \%\) of boys enrolled for track events and \(44 \%\) of boys enrolled for water sports. Also, \(45 \%\) of girls enrolled for track events and 55\% of girls enrolled for water sports. Would it be appropriate to do a two-proportion z-test to determine whether the proportions of boys and girls enrolling for track events were significantly different (assuming we know the number of boy and girl students)? Explain.

A taste test is done to see whether a person can tell Coke from Pepsi. In each case, 20 random and independent trials are done (half with Pepsi and half with Coke) in which the person determines whether she or he is drinking Coke or Pepsi. One person gets 13 right out of 20 trials. Which of the following is the correct figure to test the hypothesis that the person can tell the difference? Explain your choice.

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