What Difference Does a Day Make?

Missing data in daily diaries Why do we sometimes collect data from patients daily, rather than weekly or monthly? One of the main reasons is variability in the patient’s condition. Take the example of asthma. Over a week or a month, an asthma sufferer may experience...

How reliable can a single item be?

Meet Joanne. Jo has a nasty and persistent foot fungus, so agrees to take part in the trial of a new fungal cream. She is given a questionnaire and asked to rate her fungal problem on a 0-10 scale at the start of the trial, and then again when it’s over. At that...