A confidence interval (CI) is a range used of values that help describe the reliability of research data. A narrow range of values shows high precision and credibility, whereas a wide interval would suggest the opposite. CIs are calculated at a confidence percentage level, with 95% used most often.

Example: In our Sigma Statement on Red Meat, you'll see the following line:

"Comparing the highest vs. lowest intake of red meat found a 31% relative risk increase for all-cause mortality (95% CI 1.27-1.35)"

Here a confidence interval is given for the relative risk of 1.31 (i.e. 31% increased risk). The CI is between 1.27 and 1.35 (or an increased risk of 27-35%). This range is where there is 95% certainty that the true relative risk would lie.

The hazard ratio is the ratio of:
(probability of an event occurring in treatment group) ÷ (probability of an event occurring in control group)

A hazard ratio (HR) of 1 means lack of association, a hazard ratio greater than 1 suggests an increased risk, and a hazard ratio below 1 suggests a smaller risk.

Expression of how risk changes with a particular behaviour or intervention. Can be determined by comparing the absolute risk in an intervention group to the control group, for example. So it states the probability that one group/condition will experience an outcome/event compared to people in another group.

Example: In our Sigma Statement on Red Meat, you'll see the following line:

"Comparing the highest vs. lowest intake of red meat found a 31% relative risk increase for all-cause mortality (95% CI 1.27-1.35)"

Here the risk of all-cause mortality changes as you move from the lowest to highest intake. A relative risk (RR) of 1.31 tells us that those eating the highest intakes have a 31% higher risk compared to those at the lowest intakes.