Your Guide To Critical Appraisals In A Job

1.

Of 400 patients who received the flu vaccination and 379 patients who had not, 19 and 30 (respectively) developed the flu during the 12 month follow up. Select the study design that best suits this scenario

A.

Systematic review
B.

Randomised Controlled Trial
C.

Cohort Study
D.

Case-control Study

Correct Answer
C. Cohort Study

Explanation
A cohort study would be the most appropriate study design for this scenario. In a cohort study, a group of individuals who share a common characteristic (in this case, receiving the flu vaccination or not) are followed over time to observe the development of a particular outcome (in this case, developing the flu). In this scenario, the researchers followed a group of 400 patients who received the flu vaccination and 379 patients who did not, and observed the development of the flu in both groups over a 12-month follow-up period. This type of study design allows for the comparison of outcomes between exposed and unexposed groups and can help determine the effectiveness of the flu vaccination in preventing the flu.

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2.

A study to test the relationship between chocolate and the development of cardiovascular disease reports that the relationship is not statistically significant at the 5% level with p = 0.11 Based solely on this p value, it would be appropriate to report that:

A.

Chocolate is not related to cardiovascular disease
B.

The study has failed to demonstrate a relationship but the existence of a relationship cannot be ruled out
C.

If the study included fewer patients, the relationship would probably have met the criteria for significance.
D.

We must avoid eating chocolate

Correct Answer
B. The study has failed to demonstrate a relationship but the existence of a relationship cannot be ruled out

Explanation
Based on the p-value of 0.11, which is greater than the commonly used significance level of 0.05, it would be appropriate to report that the study has failed to demonstrate a statistically significant relationship between chocolate and cardiovascular disease. However, it is important to note that the existence of a relationship cannot be completely ruled out. This means that there may still be a potential relationship between chocolate and cardiovascular disease, but the study did not have enough evidence to support it.

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3.

A 95% Confidence Interval provides information about:

A.

Whether a result is statistically significant or not
B.

Provides an upper bound for the effect size
C.

Whether the result is clinically significant or not
D.

All of the above

Correct Answer
D. All of the above

Explanation
A 95% Confidence Interval provides information about whether a result is statistically significant or not, as it indicates the range within which the true population parameter is likely to fall. It also provides an upper bound for the effect size, giving an estimate of the maximum magnitude of the effect. Additionally, it helps determine whether the result is clinically significant or not, as it provides a range of values that can be used to assess the practical importance of the findings. Therefore, all of the given options are correct explanations for what a 95% Confidence Interval provides information about.

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4.

Select True or False: Randomised Controlled Trial (RCT) is the best design for studies on effectiveness of a therapy

A.

True
B.

False

Correct Answer
A. True

Explanation
Randomised Controlled Trial (RCT) is considered the gold standard design for studies on the effectiveness of a therapy. This is because RCTs involve randomly assigning participants into different groups, with one group receiving the therapy being studied and the other group receiving a placebo or an alternative treatment. By randomly assigning participants, RCTs help to minimize bias and ensure that any observed differences in outcomes between the groups can be attributed to the therapy being studied. RCTs also often include blinding, where neither the participants nor the researchers know which group they are in, further reducing bias. Overall, RCTs provide strong evidence for the effectiveness of a therapy.

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5.

Patients should be analysed in the groups to which they were randomised (i.e. intention-to-treat analysis), regardless of whether they actually received the treatment or not

A.

True
B.

False

Correct Answer
A. True

Explanation
In clinical trials, it is important to analyze patients based on the group they were randomly assigned to, regardless of whether they actually received the treatment or not. This is known as intention-to-treat analysis. It helps to maintain the integrity of the study design and prevents bias in the results. By analyzing patients based on their assigned group, researchers can assess the true effectiveness and safety of the treatment, as it reflects real-world conditions where not all patients may adhere to the treatment protocol.

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6.

A result is NOT statistically significant if the 95% confidence interval of the relative risk crosses the value "1"

A.

True
B.

False

Correct Answer
A. True

Explanation
If the 95% confidence interval of the relative risk crosses the value "1", it means that there is a possibility that the true relative risk is equal to 1. This indicates that there is no significant difference between the two groups being compared. Therefore, the result is not statistically significant.

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7.

An outcome is NOT statistically significant if the 95% confidence interval of the absolute risk reduction crosses the value “0”

A.

True
B.

False

Correct Answer
A. True

Explanation
If the 95% confidence interval of the absolute risk reduction crosses the value "0", it means that there is a possibility that the true effect size is zero or that there is no significant difference between the groups being compared. In other words, the observed outcome is not statistically significant because it falls within the range of random chance. Therefore, the statement "An outcome is NOT statistically significant if the 95% confidence interval of the absolute risk reduction crosses the value '0'" is true.

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