Interrupted time series analysis (ITS), sometimes known as quasi-experimental time series analysis, is a method of
statistical analysis
Statistical inference is the process of using data analysis to infer properties of an underlying distribution of probability.Upton, G., Cook, I. (2008) ''Oxford Dictionary of Statistics'', OUP. . Inferential statistical analysis infers propertie ...
involving tracking a long-term period before and after a point of intervention to assess the intervention's effects. The
time series refers to the data over the period, while the interruption is the intervention, which is a controlled external influence or set of influences.
Effects of the intervention are evaluated by changes in the level and slope of the time series and
statistical significance
In statistical hypothesis testing, a result has statistical significance when it is very unlikely to have occurred given the null hypothesis (simply by chance alone). More precisely, a study's defined significance level, denoted by \alpha, is the p ...
of the intervention parameters. Interrupted time series design is the
design of experiments based on the interrupted time series approach.
The method is used in various areas of research, such as:
*
political science: impact of changes in laws on the behavior of people;
[ (e.g., Effectiveness of sex offender registration policies in the United States)
* economics: impact of changes in credit controls on borrowing behavior;][
* sociology: impact of experiments in income maintenance on the behavior of participants in welfare programs;][
* history: impact of major historical events on the behavior of those affected by the events;][
* psychology: impact of expressing emotional experiences on online content;
* medicine: in medical research, ]medical treatment
A therapy or medical treatment (often abbreviated tx, Tx, or Tx) is the attempted remediation of a health problem, usually following a medical diagnosis.
As a rule, each therapy has indications and contraindications. There are many different ...
is an intervention whose effect are to be studied;
* marketing research: to analyze the effect of "designed market interventions" (e.g., advertising) on sales.
The ITS design is the base of the comparative time series design, whereby there is a control series and an interrupted series, and the effect of an intervention is confirmed by the control series.[''The Design and Analysis of Research Studies'']
p. 168
See also
* Quasi-experimental design
References
Time series
Quantitative research
Design of experiments
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