What is a cross-sectional study?

Every investigation requires an action plan that allows obtaining the necessary information to respond to the problem statement. This plan is known as research design, among which experimental and non-experimental or observational designs stand out.

Among the experimental ones we find the pre-experimental study, the quasi-experiments and the pure experiments. On the other hand, in observational designs we can find the cross-sectional or transectional study and the longitudinal or evolutionary study.

Cross-sectional studies belong to a much broader category of research designs, in which the researcher must visualize in a very practical and concrete way how they will answer their research questions and how they will approach meeting the objectives of their work.

What is a cross-sectional study?

The cross-sectional study is a type of non-experimental research design in which data collection is carried out in a single period of time. In this type of study, as in all observational designs, there is no intervention on the variables, they are not influenced, they are only observed.

We can affirm that the purpose of the cross-sectional design is describe variables and analyze their incidence and interrelation at a given time (Hernández-Sampieri, 2014). For example:

To measure the attitude of fourth grade students who failed the evaluative exams in the last month of the academic calendar. To measure the level of job satisfaction of the employees of an automotive company. To investigate the relationship between attraction and trust during courtship in couples of young people.Analyze which population (men or women) buys more sports clothing in an online store during a week.

Cross-sectional studies can encompass various groups of people, objects, phenomena, events, and situations. But data collection is always carried out at a single moment. The transversal meaning of all research corresponds to a single measurement over a period of time.in which it is planned to analyze the variables or the association relationship between them (Cvetkovic-Vega et al., 2021).

Characteristics

One of the main characteristics of cross-sectional studies is that are done in a single moment. Unlike longitudinal studies, where data information is collected at different times and where the evolution of the values ​​in the variables is analyzed throughout said period, in transectional studies the evolution is not analyzed. It is a snapshot at a specific moment.

Another characteristic of these designs is that They do not manipulate the variables. Being a variant of the observational design, the only aim is to describe, correlate or explore one or more variables. Manipulation of variables is never carried out as in experimental research designs.

Cross-sectional studies allow the researcher observe numerous features at the same time, but always in a specific period. This also allows the study to provide information about what is happening currently.

Types of cross-sectional studies

There are different types of cross-sectional studies. They are the following:

Exploratory cross-sectional studies

They aim know a variable, or a set of them, a community, a context, an event, a situation that are little known. This initial scan is carried out at a specific time. They are generally applied to new research problems (Hernández-Sampieri, 2014).

Descriptive cross-sectional studies

Its purpose is to learn more about the incidence of the modalities of one or more variables in a population and provide a description. They are, therefore, purely descriptive studies and when they formulate their respective hypotheses, these are also descriptive.

Cross-sectional correlational studies

This type of design describes the association between two or more categories, concepts or variables at a given time. This study is only limited to establishing relationships, without talking about causes and effects.

How to start a cross-sectional study

To start a cross-sectional study, the following four steps can be applied, according to Álvarez-Hernández and Delgado-De la Mora (2015):

Pose a research question and delimit the study population, carefully choosing the study sample through rigorous sampling.Decide which variables are relevant for the research question, in accordance with published scientific evidence.Choose measurement method of the variables, the data collection procedures and the type of sources that will be consulted.Select the data analysis plan obtained, clearly establishing the statistical procedures.

Advantages and disadvantages of cross-sectional studies

Among the advantages of cross-sectional studies we can find the following (Levin, 2006):

They are relatively inexpensive and it takes little time to perform them. They allow us to estimate the prevalence of the outcome of interest, since the sample is generally taken from the entire population.Various outcomes and risk factors can be evaluated.They are very useful for public health planning, understanding the etiology of diseases and for generating hypotheses.No losses to follow-upsince only a single measurement is made.

As disadvantages of these types of designs we can find (Levin, 2006) the following:

It is impossible to make causal inferences and establish directionality of associations. Because only a single measurement is made at a specific time, the situation may yield different results if another time frame had been chosen.Prevalence-incidence bias (also called Neyman bias). Especially in the case of longer-term illnesses, any risk factors leading to death will be underrepresented among those with the illness.Risk cannot be measured objectively nor make reliable forecasts.

In this article we have described a type of study widely used in research due to its power at a descriptive level and its low cutoff in comparison, for example, to a longitudinal study. In many cases, they are also used to carry out a pre-analysis, with the aim of assessing whether it is worth doing an experimental study.

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