Confidence intervals (CIs) are an effective means of quantifying the uncertainty inherent in study results. Alongside considerations of possible sources of bias in the study design, CIs describe the extent to which study results are applicable in general, beyond the participants involved in the study. We discuss CI use and interpretation for some commonly encountered study designs. We highlight a close relation between CIs and p-values, such that presentation of 95% CIs can make it redundant to state whether a corresponding p-value is less than 0.05. We encourage researchers to use CIs to present their research findings, rather than relying on p-values alone.