QuestionSBA
QuestionChoice
The NNT is calculated by taking the reciprocal of the absolute risk reduction. In this case, it would be 1/(22.4% - 14%) = 1/(8.4%) = 12
32052
e
The number needed to treat (NNT) to prevent one cardiovascular event on rosuvastatin is 8
QuestionChoice
ARR is calculated by taking the absolute risk (AR) of the placebo group and subtracting from it the AR of the therapeutic group. In this case, ARR = 5.0% - 4.4% = 0.6%
32050
c
The absolute risk reduction (ARR) of death from non-cardiovascular causes is 0.88
QuestionChoice
The relative risk reduction is calculated by taking the difference between the absolute risk in the control and therapeutic groups and dividing it by the absolute risk of the control group. In this case, it would be (22.4 - 14) / 22.4 = 37.5%
32048
a
The relative risk reduction of cardiovascular events for patients on rosuvastatin is 37.5%
QuestionChoice
Confidence interval (CI) is a measure of how confident the study's authors are that the true population value lies within a particular range, and it is usually 95%. If the confidence interval does not include the null hypothesis value (for relative risk, this value is 1), we can say a statistically significant difference exists. In this case, as the CI is from 0.75 - 1.10 and includes 1, there is no significant reduction in death from all causes
32049
b
There is a statistically significant reduction in death from all causes in patients on rosuvastatin
QuestionChoice
Confidence interval (CI) is a measure of how confident the study's authors are that the true population value lies within a particular range, and it is usually 95%. If the confidence interval does not include the null hypothesis value (for relative risk, this value is 1), we can say a statistically significant difference exists. In this case, as the CI is from 0.75 - 1.10 and includes 1, there is no significant reduction in death from all causes
32051
d
There is no statistically significant reduction in cardiovascular events, (including death) in patients on rosuvastatin
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i refuse.
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# Definition

Risk in medical statistics refers to the probability of an outcome (either good or bad) occurring within a studied population. There are several different types of risk that are often used in medical studies.

# What is Risk/Prevalence?

This is simply the probability of an event occurring within a defined population.

# What is Risk Ratio (RR)?

The risk ratio (also known as relative risk) is the probability of an event occurring in an exposed group compared to the probability occurring in a non-exposed group.

The risk ratio is calculated by finding the ratio of incidence of a disease amongst the exposed population and the incidence amongst the non-exposed population.

Risk ratios are used in cohort studies and in interventional studies in which the experimenter intervenes at some point during the study, such as in randomised controlled trials and pre-post studies.

However, in cross-sectional studies and case-control studies, the incidence of the disease in the exposed and unexposed populations cannot be found, since the data only provides the cases and controls.

Consequently,the risk ratio cannot be calculated for case-control studies and cross-sectional studies. Instead, an odds ratio must be found.

# What is Absolute Risk Reduction (ARR)?

The absolute risk reduction is the absolute difference in the risk between the control group and the experimental group. It tells you in absolute terms how much an intervention changes an outcome of interest.

# Calculation of Absolute Risk Reduction

It is calculated as follows:

_ARR = Risk(control group) - Risk(experimental group)_

A given ARR is generally considered significant if the 95% confidence interval does not cross 0.

ARR can then be used to calculate the number needed to treat (NNT).

# What is Relative Risk Reduction (RRR)?

The relative risk reduction can be thought of as the proportional reduction in risk bestowed by the intervention compared to the control situation. It is more useful in helping you understand the efficacy of an intervention when the absolute risk of outcomes are rare (for example when considering the benefits of a statin for reducing MI in a given population).

# Calculating RRR

It is calculated as follows:

_RRR = 1 - [Risk(Experimental group) / Risk(Control group)]_

A given RRR is generally considered significant if the 95% confidence interval does not cross 1.
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Risk
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Medical Statistics
The relative risk reduction of cardiovascular events for patients on rosuvastatin is 37.5%
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Relative Risk Reduction (RRR) is a measure used to compare the risk of an event between two groups. It is calculated by taking the difference between the absolute risk in the control and therapeutic groups and dividing it by the absolute risk of the control group.
A 50-year-old gentleman is admitted to the Cardiology ward having suffered a myocardial infarction. He is started on numerous medications for secondary prevention and has done some reading up whilst recuperating on the ward. In particular, he some questions regarding rosuvastatin as he has heard that it is a highly effective drug.


He would like to discuss a study he read in a journal. The data is as follows:


|Outcome|Rosuvastatin group<br />(N=2500)|Placebo group<br />(N=2500)|Relative Risk <br />(95% CI)|
|---------------------------------------|--------------------------------|---------------------------|----------------------------|
|Cardiovascular events (including death)|350 (14%)|560 (22.4%)|0.63 (0.59 - 0.72)|
|Death from non- cardiovascular causes|110 (4.4%)|125 (5.0%)|0.88 (0.80 - 1.05)|
|Death from any cause|270 (10.8%)|325 (13.0%)|0.83 (0.75 - 1.10)|


 _N (Total number of people in the group), CI (Confidence Interval)_


Which of the following is true based on the data above?
a