Longitudinal studies — aikyam school

What it means

A study that checks the same group of people at different times. This lets researchers examine how things change over time.

Examples on this page are illustrations, not findings from the research cards.

Worked example

Researchers ask the same workers about their wellbeing at the start, after three months and after six months.

Hypothetical example: three volunteers rate their sleep from 0 to 10. At the first survey their scores are 2, 4 and 6. Three months later, the same volunteers report 4, 4 and 7. Researchers can match each person's later score with that person's starting score.

The first volunteer's score rose by 2 points, the second stayed the same and the third rose by 1. These repeated observations describe individual change. Without an appropriate study design and comparison, they do not show why the changes happened.

A closer look

A longitudinal study observes the same group of people at different times. This helps researchers examine the order of events and how individuals' circumstances change. For example, they might measure work, health or savings at the start and return several times over the following year. The repeated measurements connect later information with an earlier picture of the same participants.

This differs from separate surveys that question a new group each time: a changing average in those surveys might partly reflect different people answering. Following the same people makes individual change easier to examine, but it does not explain its cause on its own. Other events can occur between surveys, and people who stop responding can change the picture.

A common misunderstanding

Following people over time does not, by itself, establish cause and effect or mean they were randomly assigned to a programme.

Check the explanation

Sources

The wording and examples are original explanations informed by these references.

Cite this explanation

Longitudinal study. aikyam school. https://aikyam.school/glossary/longitudinal/

Used in these cards

60 cards use this term

The original research wording is preserved in these cards.