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Why are crude mortality rates often misleading when comparing two populations?

In an RCT comparing a new pain reliever to a placebo, 300 participants were randomized evenly between the treatment and control groups. After the trial, 90 participants in the treatment group reported pain relief, while 45 participants in the control group reported pain relief. Calculate the odds ratio (OR) of pain relief for the treatment group compared to the control group.

The multiplication rule for independent events can be applied when:

In a cross-sectional study, 800 individuals were surveyed. Of these, 200 were found to have hypertension. Of the hypertensive individuals, 50 were smokers. The prevalence of smoking in the general population is 25%. Calculate the prevalence ratio (PR) of smoking in hypertensive individuals compared to the general population.

In the UK in 2015, the male population was approximately 31,000,000, of which 2,064,600 were obese. Calculate the prevalence of obesity in this population, expressed as a percentage.

What is the main purpose of randomization in clinical trials?

Prevalence is best defined as:

If the incidence rate ratio (IRR) for rheumatoid arthritis between women and men in a general practice is 2.8, and the incidence rate for men is 50 per 100,000 person-years, what is the incidence rate for women?

Calculate the crude incidence rate of colorectal cancer for males in England in 2015, given the number of new cases was 19,178 and the population at risk was 26,635,350. Express your answer per 100,000 people.

Which of the following is a key characteristic of an observational study?