15 Questions
What is the definition of prevalence in statistics?
The total number of cases suffering from a disorder
What is the primary purpose of hypothesis testing in statistics?
To decide whether the findings of an investigation reflect chance or real effect
What does a p-value of 0.03 indicate in a statistical test?
The result is statistically significant
What does it mean if the 95% confidence intervals of two groups do not overlap?
The result is statistically significant
What is the definition of incidence in statistics?
The number of new cases of a disorder within a specific time period
What is the concept of power in statistical significance?
The ability to detect a difference due to the sample size
What is the Relative Risk (RR) of a bad outcome in the intervention group if the event rate is 12% in the intervention group and 20% in the control group?
0.6
What is the Absolute Risk Reduction (ARR) if the risk of a bad outcome is reduced from 20% to 12%?
8%
What is the Relative Risk Reduction (RRR) if the Relative Risk (RR) is 0.6?
40%
What happens when outcomes occur infrequently?
You can see a large difference between the Absolute Risk Reduction (ARR) and the Relative Risk Reduction (RRR)
What is the primary purpose of a surrogate outcome?
To predict the effect on a true outcome
What is the interpretation of an odds ratio (OR) equal to 1?
Exposure does not affect the likelihood of the outcome
What is the primary limitation of statistical significance?
It is heavily dependent on sample size
What is the difference between clinical significance and statistical significance?
Clinical significance is related to the extent of change, while statistical significance is related to sample size
What is the purpose of validating a surrogate outcome?
To show it predicts the true outcome
Study Notes
Statistics Case 10: ANM 150
Objectives
- Define terms: sample, population, incidence, prevalence, and more
- Describe the process of hypothesis testing and assessing statistical significance
- Interpret Relative and Absolute Risk, Odds ratio, number needed to treat/harm, and power
- Differentiate between clinical and surrogate outcomes and their respective strengths
Terminology
- Population: the entire group of people being studied
- Sample: a subset of the population
Prevalence and Incidence
- Prevalence: the total number of cases suffering from a disorder
- Incidence: the number of new cases suffering from a disorder
- Example: 26,630 people in Ontario are HIV positive (prevalence), and 1,620 people were newly infected with HIV in Ontario (incidence)
Hypothesis Testing
- The process of deciding whether the findings of an investigation reflect chance or real effect
- Statistical significance: determining whether the difference between groups is real or due to chance
Statistical Significance: P-Value and Confidence Interval
- P-value: the probability that the difference is due to chance
- P-value < 0.05: significant difference (less than 5% likelihood of chance)
- P-value > 0.05: not significant
- 95% Confidence Interval (CI): a range of values within which the true result is likely to lie
Relative Risk and Risk Reduction
- Relative Risk (RR): the probability of a bad outcome in the intervention group divided by the probability of a bad outcome in the control group
- RR > 1: increased risk of bad outcome with treatment
- RR < 1: decreased risk of bad outcome with treatment
- Relative Risk Reduction (RRR): the proportion of reduction in risk of bad outcome
- Absolute Risk Reduction (ARR): the absolute difference in risk of bad outcome between treatment and control groups
Odds Ratio
- Odds Ratio (OR): the relationship between an exposure and an outcome
- OR = 1: exposure does not affect the likelihood of the outcome
- OR > 1: exposure associated with increased likelihood of the outcome
- OR < 1: exposure associated with decreased likelihood of the outcome
Outcomes
- Clinical Outcomes: a clinical event (e.g., stroke, suicide, hip fracture)
- Surrogate Outcomes: an indicator that can be observed sooner, at a lower cost, or less invasively (e.g., biomarkers, indicators of disease progression)
Statistical Significance vs. Clinical Significance
- Statistical Significance: the difference is not due to chance (p-value < 0.05)
- Clinical Significance: the intervention has a genuine, measurable effect that makes a real difference in the lives of patients
Power
- The ability of a study to detect a real difference between two groups
- Depends on sample size and the magnitude of the effect
This quiz covers key concepts in statistics, including terms, hypothesis testing, and interpretation of statistical measures such as risk and odds ratio. Test your understanding of population, sample, and outcome types.
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