Suggested searches

Looking for a free online survey tool? offers a general survey tool with standard question types, randomisation blocks and multilingual support. Always free.

Get started for free
Request consultation

Do you need support in running a pricing or product study? We can help you with agile consumer research and conjoint analysis.

Request consultation

Time in Research

Time is an important element of any research design, and here I want to introduce one of the most fundamental distinctions in research design nomenclature: cross-sectional versus longitudinal studies. A cross-sectional study is one that takes place at a single point in time. In effect, we are taking a ‘slice’ or cross-section of whatever it is we’re observing or measuring. A longitudinal study is one that takes place over time – we have at least two (and often more) waves of measurement in a longitudinal design.

A further distinction is made between two types of longitudinal designs: repeated measures and time series. There is no universally agreed upon rule for distinguishing these two terms, but in general, if you have two or a few waves of measurement, you are using a repeated measures design. If you have many waves of measurement over time, you have a time series. How many is ‘many’? Usually, we wouldn’t use the term time series unless we had at least twenty waves of measurement, and often far more. Sometimes the way we distinguish these is with the analysis methods we would use. Time series analysis requires that you have at least twenty or so observations. Repeated measures analyses (like repeated measures ANOVA) aren’t often used with as many as twenty waves of measurement.