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In a study of malpractice claims where a settlement had been reached, two random samples were selected: a random sample of 515 closed malpractice claims that were found not to involve medical errors and a random sample of 889 claims that were found to involve errors (New England journal of Medicine \(12006 \mathrm{l}\) : \(2024-2033) .\) The following statement appeared in the referenced paper: "When claims not involving errors were compensated, payments were significantly lower on average than were payments for claims involving errors \((\$ 313,205\) vs. \(\$ 521,560, P=0.004) . "\) a. What hypotheses must the researchers have tested in order to reach the stated conclusion? b. Which of the following could have been the value of the test statistic for the hypothesis test? Explain your reasoning. i. \(t=5.00\) ii. \(t=2.65\) iii. \(t=2.33\) iv. \(t=1.47\)

Short Answer

Expert verified
The researchers must have tested the following hypotheses: \(H_0: µ_1 = µ_2\) (null hypothesis) and \(H_A: µ_1 > µ_2\) (alternative hypothesis). Looking at the presented test statistic options, \(t=5.00\) could have been the test statistic for this hypothesis test due to the low p-value indicating a high absolute t-score.

Step by step solution

01

Identifying the Hypotheses

The scenario suggests there's a significant difference in the average payments for malpractice claims involving errors and those not involving errors. Therefore, the null hypothesis (\(H_0\)) would be that the average payment for claims with errors (\(µ_1\)) is equal to the average payment for claims without errors (\(µ_2\)). It can be written as: \(H_0: µ_1 = µ_2\) The alternative hypothesis (\(H_A\)), which is what the researchers are attempting to prove, would be that the average payment for claims with errors is higher than the average payment for claims without errors. So, \(H_A: µ_1 > µ_2\).
02

Analyzing Potential Test Statistics

The value of the test statistic is based on the data and the null hypothesis. In this case, it would likely be a t-score because the standard deviations of the populations are likely unknown. Assuming the researchers used a one-tailed test because they were testing if one mean is greater than the other (and not simply if they are different), and also assuming the sample size is sufficiently large, then a t-score greater than 1.96 or less than -1.96 would lead to rejection of the null hypothesis at the 0.05 significance level. If the p-value provided (\(P=0.004\)) is matched with the t-distribution table, it further implies a large absolute t-value, thus, potentially it should be a high t-score.
03

Selecting the Correct Test Statistic Value

Looking at the 4 t-score values offered, \(t=5.00\) is the one with the highest absolute value. Given the significant p-value of 0.004, which would require a high absolute t-score to achieve, we conclude that \(t=5.00\) could have been the test statistic for this hypothesis test.

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Key Concepts

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

Null Hypothesis
When venturing into the realm of hypothesis testing, one must first understand the concept of the null hypothesis (\textbf{H\textsubscript{0}}). This is the default stance or the 'starting point' assumption made prior to conducting a statistical test. It traditionally suggests that there is no effect or no difference in the population — or more specifically, it postulates that any observed differences in sample data are purely due to chance.

In the context of malpractice claims, if researchers were examining the average settlements for claims with and without medical errors, the null hypothesis would claim that these two groups do not differ - that is, the average settlement amount for both groups is the same. Mathematically, this can be express as: \(H_0: µ_1 = µ_2\), where \(µ_1\) and \(µ_2\) represent the mean payments for claims with errors and without errors, respectively.
Alternative Hypothesis
Contrasting the null hypothesis, the alternative hypothesis (\textbf{H\textsubscript{A}} or \textbf{H\textsubscript{1}}) represents what the researchers are truly attempting to support. It's an assertion that there is a statistically significant effect or difference — it offers the alternative scenario to the null hypothesis.

In the malpractice claims study, the alternative hypothesis would suggest that the average payments for claims involving medical errors are greater than those claims without errors. Formulating this concept can be encapsulated as: \(H_A: µ_1 > µ_2\). If the test results show that the null hypothesis can be rejected, this would lend support to the alternative hypothesis.
T-Statistic
The t-statistic is a type of test statistic that follows a t-distribution under the null hypothesis. It's a measure of how many standard deviations our sample statistic is from the population parameter stated in the null hypothesis. This metric is particularly useful when dealing with small sample sizes or when the population standard deviation is unknown, which is often the case.

Given the information within the malpractice claims study, such a t-statistic would help determine if the observed difference in average payments between the two groups is statistically significant. A very high positive or very low negative t-statistic could indicate a rejection of the null hypothesis, leaning toward accepting the alternative hypothesis.
P-Value
Diving deeper into statistical testing, the p-value stands as a pivotal figure. It is the probability of observing a test statistic at least as extreme as the one obtained, assuming that the null hypothesis is true. If the p-value is lower than the predetermined significance level (often \(\alpha = 0.05\)), the result is deemed 'statistically significant,' prompting the rejection of the null hypothesis.

In the case of the malpractice claims study, the p-value of 0.004 is well below the standard cutoff of 0.05. This small p-value indicates strong evidence against the null hypothesis, suggesting significant differences in average payments between claims with errors and those without.
Malpractice Claims
Malpractice claims are important legal and medical considerations, as they involve allegations of inadequate or negligent care from healthcare providers. In the context of the exercise, these claims can be categorically split into those with medical errors and those without.

Analyzing such data for possible differences in financial settlements via hypothesis testing allows for quantifying whether malpractice claims with confirmed errors result in higher average payments. Understanding these patterns can help in policy making and improving patient care standards.
Statistical Significance
Statistical significance is the likelihood that a relationship or a finding is caused by something other than mere random chance. This concept is crucial in hypothesis testing as it helps us gauge the strength of the evidence against the null hypothesis.

A statistically significant result in the malpractice claims study, indicated by the low p-value, tells us that the difference in payment amounts between claims involving errors and those without is unlikely due to randomness or sampling variability and, therefore, may reflect a true difference in the population.

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Most popular questions from this chapter

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