A Non-Scientists Guide to Understanding Studies [3 types of scientific studies Included]

A Non-Scientist Guide to Understanding and Reading Studies

In today’s world, it is extremely common for people with access to the internet to look up any unusual symptoms they may be experiencing. Aside from potentially increasing your anxiety with all of this new information, being able to access relevant scientific information allows us to become more informed patients.

In fact, health literacy, which describes an individual’s ability to obtain, process and understanding basic health information 1, has been recognized as an essential part of successful patient outcomes.

Aside from Google searches that lead you to websites like WebMD, News-Medical.net and other useful websites like this one, it is also important for the informed patient to be able to read and understand the information provided in scientific articles.

While this may seem like a simple task to achieve, reading a scientific article can be extremely complex and difficult to understand. This guide will help you better understand the research process that leads scientists to their results, as well as the best way to approach reading and understanding the information discussed in scientific articles.

What is the Scientific Method?

Every scientific article is based on a series of steps that can be related to a process otherwise referred to as the Scientific Method. The scientific method begins with a question, which is followed by several subsequent steps that allow researchers to recognize the background information and tools they will need to ultimately find the correct answer to that question. See Figure 1 below for more information on how the Scientific Method is conducted in any research setting.

Scientific Method

Figure 1: The steps of the Scientific Method.

Every step of the scientific method is performed as a collaborative effort that must be well-documented by every researcher involved in the study. By recording all observations and maintaining accurate documentation of all experiments, regardless of how the results come out, researchers are able to share their scientific findings to people around the world who are interested in the same topic.

How do Scientists Conduct Research?


All scientific experiments can be better understood as cause and effect relationships between all involved parts. In this relationship, variables can be thought of as the cause, and the effect of your changing variable ultimately plays a role in answering the initial question that brought you to this study in the first place.

Variables are an important aspect of almost every scientific experiment. A variable describes any aspect of the experiment that can be controlled, changed or measured. Therefore, choosing appropriate variables in any experiment plays a crucial in determining the outcome and reliability of your experiment.

In any scientific experiment, researchers will typically make some type of change to the independent variable, whereas all other factors of the experiment will be constant. For example, if the ability of a new herbal treatment to treat diarrhea is being tested, the independent variable would be the amount of the herb that is given to the patients, whereas the controlled variable would be the herb’s ability to stop diarrhea from occurring. The different types of variables that can be included in any scientific study are further discussed in Figure 2.

Types of variables in scientific studies

Figure 2: Variables involved in scientific experiments 2.

Different Types of Scientific Studies

There are three major types of experimental research designs:

  1. Pre-Experimental Design
  2. True Experimental Design
  3. Quasi-Experimental Design

These designs include various types and elements that play a role in determining the success of each experiment.

Experimental Research Designs

Figure 3. Different types of scientific study design 3,4,5.

Understanding Clinical Research

Before any type of drug, treatment or vaccination can be administered to human beings, an extensive series of experiments involved in the pre-clinical testing stages must first be performed.

While animal testing is a controversial subject, it is necessary for any drug or vaccine to be tested in animals to determine whether there is any actual benefit of the drug and any potential side effects that can be expected if this drug continues to human clinical trials.

Preclinical Studies

Choosing a preclinical model that closely relates the human disease that you are interested in treating plays a crucial role in determining the success of your studies, as well as the ability of your tested drug or treatment to continue onto the next stages of clinical research. This stage of scientific research, which is typically conducted by testing the drug or treatment out on cells and eventually some type of animal model, aims to answer the following questions:


  • How potent is the drug?
  • How effective is this drug in treating symptoms?
  • Does this drug cause any toxicity that outweighs its therapeutic benefits?


  • How much of the drug is absorbed by the body after taken?
  • Are there any unwanted interactions that occur between the drug and the various molecules that exist in our bodies?
  • How much of the drug is eliminated (either through urination or defecation)? Is this rate of elimination too fast or too slow?


  • What organs can be affected negatively by this drug?
  • Does this drug cause any unwanted effects?
    • Is it a carcinogen? (Does it cause cancer?)6

Cell Studies (In vitro)

Cell studies

In vitro, which translates to “in glass” as a way to refer to the Petri glasses that have been traditionally used to contain cell cultures, are extremely important scientific studies. As a relatively fast, simple and cost-effective investigation method, in vitro models provide useful information on the way in which drugs behave when exposed to a specific type of cell type or tissue.

What this type of experimental model provides is important for establishing preliminary data, it is limited in its ability to determine how drugs will interact with other cells of the body. As a result, when a drug appears to exhibit beneficial effects in vitro, scientific researchers will typically continue to expand their work to relevant in vivo models.

Animal Studies (In vivo)

Animal studies

In vivo, which translates into “in living [organisms],” is one of the most controversial aspects of scientific research, but is also one of the most important aspects that allow new and potentially curing drugs to arise. Prior to beginning their studies on animals, researchers must carefully choose species-specific physiology and other similarities in regard to the target organ of their treatment to ensure that their experiments are scientifically valid 6.

Animal research is highly regulated by the government, as well as within the institution where the research is being performed. It is very common for in vivo experiments to be performed in rodent species such as mice, rats, guinea pigs and hamsters; however, other animals can also be used if the treatment warrants its use.

Clinical Trials (Human Studies)

clinical studies

After preclinical testing has been completed, there are various phases that researchers must go through before any drug, treatment or vaccine can be considered to enter the market. The various stages of clinical research are described below:

  • Investigational New Drug Application (IND)

    • Describes the results of pre-clinical testing
    • Defines how future studies in humans will be conducted
    • Must be reviewed and approved by the U.S. Food and Drug Administration within 30 days
  • Phase I (Assess Drug Safety)

    • Assesses the safety of the drug for humans
    • Doses to be studied in future studies are determined
    • Evaluates how humans react to the drug and any potential side effects that are expected to arise
    • Typically lasts several months up to 1 year
    • Approximately 70% of experimental drugs will pass Phase I
  • Phase II (Safety and Efficacy)

    • Uses both control groups and experimental groups to test the efficacy and safety of the drug
      • Control Group: Will either receive a placebo or standard medication for the targeted disease
      • Experimental Group: Will receive the experimental vaccine, treatment or drug
    • Can be blinded (researchers do not know who is receiving the drug or placebo)
    • Can last from several months up to 2 years
    • Approximately 30% of experimental treatments pass this stage
    • Involves 100 – 300 participants/volunteers
  • Phase III (Large Scale Testing)

    • Provides a better understanding of the following drug properties:
      • Efficacy
      • Benefits
      • Range of potential unwanted side effects
      • Compare the experimental drug to what is already used to treat the targeted condition
    • Involves 1,000 – 3,000 participants/volunteers
    • Randomized and blinded studies
    • Typically lasts several years
    • Approximately 70% to 90% of experimental treatments pass this stage of the investigation
  • Licensing (Approval to Use)

    • After each of the aforementioned stages of clinical research has been completed and approved, a New Drug Application (NDA)/Biologics License Application (BLA) will be filed with the FDA
      • Can take anywhere from 6 months to 2 years to be completed, depending upon the country’s specific requirements
  • Approval (Available for Prescription) 7

Types of Clinical Study Designs

There are four broad categories of clinical research study, each of which includes various different subtypes that further explore the specific target of each study design. These 4 study design categories include:

1. Observational Designs

    • Non-analytic (Descriptive): provides information on the prevalence or incidence of a condition that is affecting a population of patients
      1. Case Reports
      2. Case-Series
      3. Qualitative Studies
      4. Cohort Studies
      5. Surveys (cross-sectional)
    • Analytic: determines the relationship between two factors of a disease, exposure, treatment and/or outcome

2. Experimental Studies

Allows researchers to manipulate an aspect of the exposure or treatment of the subject

    • Randomized Controlled Trials (RCTs)

3. Qualitative Studies

4. Systematic Reviews

Involves extensive research that must be incorporated into any type of study design

    • Provides a justification based on previous work as to why the specific type of research is being conducted

The design of a clinical study plays a huge role in determining the overall reliability and transparency of the research. For example, studies that do not utilize a control group are considered less reliable than those that do include control groups. Additionally, the number of test subjects, which is otherwise known as the sample size, also plays a crucial role in determining how reliable the results of a study are.

For example, it is common for animal research studies to involve 8-12 animals in each treatment group, whereas clinical trials can involve as much as 3,000 patients. The success of a treatment based on a sample size of 3,000 is much more reliable than that which is conducted on a sample size of 8.

As shown in the figure below, the type of study design increases in its rigor and accuracy while reducing its susceptibility to error as you move up in the pyramid. In addition, the level of complexity of these study designs also increases as you move up the pyramid.

Clinical Research Design Types

Figure 4: Levels of clinical research study designs in decreasing levels of rigor.

Important Types of Clinical Research Designs

  1. Meta-Analysis: Combines data from various individual research studies.
    • Evaluates the efficacy of treatments that have been repeated in various studies
    • Typically used to provide an overview of the success of clinical trials
  2. Systematic Review: Critically reviews and evaluates all research studies that have been conducted on a specific clinical issue.
  3. Randomized Controlled Trial: Randomly assigns participants by two or more groups within a clinical trial.
    • Must involve at least one treatment and one control group
  4. Cohort Studies: People who currently have a specific condition are followed over time and compared to people living without that condition.
  5. Case-Control Studies: Begins with the outcomes of patients following a specific treatment/disease and evaluates the different experiences of each patient to determine the odds that future patients will experience the same symptoms/results
  6. Cross-Sectional Studies: A specific population at a single moment in time or time interval is observed and evaluated.
  7. Case Reports and Series: Evaluates a group of patients that have experienced a specific outcome of interest.
    • Does not require any control groups
  8. Animal Research Studies 9

Negatives in Scientific Studies

If the data in a scientific study does not turn out to be statistically significant, does that automatically determine that these studies were negative? In these situations, scientists are left to determine whether their study, in fact, proved to show no effect or any difference when their medication was used as compared to the standard. In these situations, it is important to remember: The Absence of Evidence is NOT Evidence of Absence 8.

What this means is that while the drug or treatment being tested did not appear to be significant, it is important for researchers to establish a threshold that designates whether the effect of their treatment was, in reality, too small to be determined as important. While this is a fairly uncomfortable area in research, the science community is hopeful that, with support from journals that are willing to publish uncertain results, researchers will be more willing to discuss this complicated subject.

Sources for IBS and SIBO Studies

There are several hundreds of different scientific journals in which researchers can submit the results for their in vitroin vivo and other types of studies for publication. If you are suffering from IBS, SIBO or any other type of gastrointestinal (GI) disorder, or you have a loved one who is and would like to help educate yourself on these disorders, there are numerous scientific journals that can help:

Put Your New Knowledge to Work

Now that you have gotten through this article (yes, I know it was a lot), you should have a much better understanding on why scientific research is conducted, the different components that make up any basic experiment, as well as the different ways in which research can be conducted. As you continue to expand your knowledge on the constantly advancing science world, your ability to truly understand what is being discussed in any scientific article will prove to be invaluable.

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