Recommended Set

13. Objectives

Explaining the purpose of the study by describing the question(s) that the research addresses, allows readers to determine if the study is relevant to them. Readers can also assess the relevance of the model organism, procedures, outcomes measured, and analysis used.

Knowing if a study is exploratory or hypothesis-testing is critical to its interpretation. A typical exploratory study may measure multiple outcomes and look for patterns in the data, or relationships that can be used to generate hypotheses. It may also be a pilot study which aims to inform the design or feasibility of larger subsequent experiments. Exploratory research helps researchers to design hypothesis-testing experiments, by choosing what variables or outcome measures to focus on in subsequent studies.

Testing a specific hypothesis has implications for both the study design and the data analysis [1,2]. For example, an experiment designed to detect a hypothesised effect will likely need to be analysed with inferential statistics, and a statistical estimation of the sample size will need to be performed a priori (see item 2 – Sample size). Hypothesis-testing studies also have a pre-defined primary outcome measure, which is used to assess the evidence in support of the specific research question (see item 6 – Outcome measures).

In contrast, exploratory research investigates many possible effects, and is likely to yield more false positive results because some will be positive by chance. Thus results from well-designed hypothesis-testing studies provide stronger evidence than those from exploratory or descriptive studies. Independent replication and meta-analysis can further increase the confidence in conclusions.

Clearly outline the objective(s) of the study, including whether it is hypothesis-testing or exploratory, or if it includes research of both types. Hypothesis-testing studies may collect additional information for exploratory purposes, it is important to distinguish which hypotheses were prespecified and which originated after data inspection, especially when reporting unanticipated effects or outcomes that were not part of the original study design.



  1. Festing MF and Altman DG (2002). Guidelines for the design and statistical analysis of experiments using laboratory animals. ILAR journal.
  2. Kimmelman J, Mogil JS and Dirnagl U (2014). Distinguishing between exploratory and confirmatory preclinical research will improve translation. PLoS Biol. doi: 10.1371/journal.pbio.1001863

Example 1

“The primary objective of this study was to investigate the cellular immune response to MSC injected into the striatum of allogeneic recipients (6-hydroxydopamine [6-OHDA]-hemilesioned rats, an animal model of Parkinson's disease [PD]), and the secondary objective was to determine the ability of these cells to prevent nigrostriatal dopamine depletion and associated motor deficits in these animals.” [1]

Example 2

“In this exploratory study, we aimed to investigate whether calcium electroporation could initiate an anticancer immune response similar to electrochemotherapy. To this end, we treated immunocompetent balb/c mice with CT26 colon tumors with calcium electroporation, electrochemotherapy, or ultrasound-based delivery of calcium or bleomycin.” [2]

Example 3

“While characterizing a rab-6.2-null C. elegans strain for another study, we observed that rab-6.2(ok2254) animals were fragile. We set out to analyze the fragile-skin phenotype in rab-6.2(ok2254) animals genetically…We observed several ruptured animals on our rab-6.2(ok2254) culture plates during normal maintenance, a phenotype very rarely observed in wild-type cultures…We hypothesized that RAB-6.2 is required for skin integrity.” [3]



  1. Camp DM, Loeffler DA, Farrah DM, Borneman JN and LeWitt PA (2009). Cellular immune response to intrastriatally implanted allogeneic bone marrow stromal cells in a rat model of Parkinson's disease. Journal of neuroinflammation. doi: 10.1186/1742-2094-6-17
  2. Falk H, Forde PF, Bay ML, Mangalanathan UM, Hojman P, Soden DM and Gehl J (2017). Calcium electroporation induces tumor eradication, long-lasting immunity and cytokine responses in the CT26 colon cancer mouse model. OncoImmunology. doi: 10.1080/2162402X.2017.1301332
  3. Kim JD, Chun AY, Mangan RJ, Brown G, Mourao Pacheco B, Doyle H, Leonard A and El Bejjani R (2019). A conserved retromer-independent function for RAB-6.2 in C. elegans epidermis integrity. J. Cell Sci. doi: 10.1242/jcs.223586