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Research Methods

Research 101

One of the secrets of science is to understand the language of science, and science’s primary language is the research study. Research studies allow scientists to communicate with one another and share results of their work. There are many different kinds of research and many varying fields of research, including psychology, sociology, biology, genetics, and medicine. Research can contribute findings that are instantly relevant, or inspire new research or approaches. 


Scientific Research as an Ongoing Process by ArchonMagnus is licensed under CC BY-SA

How do I identify a research study?

These guidelines can help you identify a research study and distinguish an article that presents the findings of a research study from other types of articles.

  • A research study must:
    • Ask a research question
    • Identify a research population or group
    • Describe a research method
    • Test or measure something
    • Summarize the results

Research studies are almost always published in peer-reviewed (scholarly) journals. The articles often contain headings similar to these: Introduction, Methods, Results, and Discussion/Conclusion (IMRaD structure).


("File:Wineglass model for IMRaD structure..png" by Tom Toyosaki is licensed under CC BY-SA 4.0)

Articles that are not research studies:

Articles that review other studies without presenting new research results are not research studies. Examples of article types that are NOT research studies include:

  • literature reviews
  • meta-analyses
  • editorials
  • case studies
  • comments or letters relating to previously-published research studies

Understanding research articles 

Individual research studies are the means of communicating scientific research.  This video (1:23 minutes) will describe the purpose and content of a research article. 

This video will show an example of a research article, describing its characteristics:

What is a research method?  

 As you read a peer-reviewed (scholarly) article, note the method(s) used by author(s) to plan and conduct their research. There are many different kinds of research methods but they all share two objectives: to assist the researcher to design his or her research in a way that enables the research question to be answered; and to enable the researcher to conduct his or her research in a systematic manner to ensure the findings are scientifically rigorous and have genuine potential for practical application. To achieve these objectives, the researcher follows a step-wise research process. 

The research process 

Research involves a systematic process that focuses on being objective and gathering a multitude of information for analysis so that the researcher can come to a conclusion. This process is used in all research and evaluation projects, regardless of the research method. 

Step 1. Develop the research question

Step 2. Gather information and resources (a literature review)

Step 3. Form hypotheses

Step 4. Select the research approach, also called a research design

  • Design determined by research question and literature review
  • Qualitative design - inductive approach ('top down' approach: results prove or disprove a theory)
  • Quantitative design - deductive approach ('bottom up' approach: generates new theory from results)
  • Mixed methods design - uses design characteristics from both qualitative and quantitative approaches

Step 4. Select a representative study population and sample size

  • Probability sampling - random selection of participants
  • Non-probability sampling - researcher determines participants (non-random)

Step 5. Collect the data

Step 6. Interpret the data and draw conclusions

Step 7. Write and publish the report in a peer-reviewed journal

  What is a hypothesis?  

A hypothesis is a tool of quantitative studies. Hypotheses (plural) are educated "guesses" or expectations about a solution to a problem, possible relationships between variables, or variable differences. It is the investigator's prediction or expectation of what the results will show made prior to data collection. 

To be complete the hypothesis must include three components:

  • The variables - dependent and independent.
  • The population - the entire group or elements who meet the sampling criteria. A sample is representative of that population.
  • The relationship between between one variable and another, for example, smoking and lung cancer.

A hypothesis should be:

  • stated in declarative form
  • consistent with known facts, previous research, and theory
  • be testable
  • a statement of relationships between variables
  • limited in scope (focused)
  • clear and concise

Examples of a hypothesis are:

  • Health Education programs influence the number of people who smoke.
  • Newspapers affect people's voting patterns.
  • Attendance at lectures influences exam marks.
  • Diet influences intelligence.

Types of hypothesis

Simple hypothesis - predicts the relationship between a single independent variable (IV) and a single dependent variable (DV).

For example:  Lower levels of exercise postpartum (IV) is associated with greater weight retention (DV).  

Complex hypothesis - predicts the relationship between two or more independent variables, and two or more dependent variables.

For example: The implementation of an evidence based protocol for urinary incontinence (IV) will result in (DV):

  •  decreased frequency of urinary incontinence episodes;
  •  decreased urine loss per episode;
  •  decreased avoidance of activities among women in ambulatory care settings.

Null hypotheses

Used when the researcher believes there is no relationship between two variables, or when there is inadequate theoretical or empirical information to state a research hypothesis.

Research design: Qualitative vs. quantitative research  

Research data can be placed into two broad categories:  quantitative or qualitative.

Quantitative data are used when a researcher is trying to quantify a problem, or address the "what" or "how many" aspects of a research question. It is data that can either be counted or compared on a numeric scale. For example, it could be the number of first year students at MCC, or the ratings on a scale of 1-4 of the quality of food served at the Bighorn Cafe. This data are usually gathered using instruments, such as a questionnaire which includes a ratings scale or a thermometer to collect weather data. Statistical analysis software, such as SPSS, is often used to analyze quantitative data.
Qualitative data describes qualities or characteristics. It is collected using questionnaires, interviews, or observation, and frequently appears in narrative form. For example, it could be notes taken during a focus group on the quality of the food at Bighorn Cafe, or responses from an open-ended questionnaire. Qualitative data may be difficult to precisely measure and analyze. The data may be in the form of descriptive words that can be examined for patterns or meaning, sometimes through the use of coding. Coding allows the researcher to categorize qualitative data to identify themes that correspond with the research questions and to perform quantitative analysis.

In this video (2:35 minutes) a research article that uses qualitative research methods is shown. The video points out how you can determine the methodology used in the article:

In this video (2:16 minutes) a research article that uses quantitative research methods is shown. The video points out how you can determine the methodology used in the article:

This chart summarizes some of the characteristics as well as differences between these two research methodologies:

Type of Research Word Clues Methods Search Terms Data Research Role
  • ethnographic study
  • field notes
  • field research
  • focus group
  • observation
  • open ended
  • phenomenological 
  • focus groups
  • interviews
  • recording behavior
  • unstructured observation

qualitative studies (CINAHL)

qualitative research (MEDLINE)

  • ideas
  • interpretive
  • narrative description
  • text-based
  • words
subjective-involved as a participant observer
  • case-control-study
  • lab experiment
  • clinical trial
  • cohort studies
  • control group
  • experimental group
  • intervention
  • randomized-controlled-trial
  • statistical
  • structured-questionnaire  
  • develops hypothesis
  • determines methodology
  • collects data
  • analyzes data
  • uses mathematical and statistical techniques to analyze data
  • quantitative studies (CINAHL)
  • MEDLINE uses headings for specific types of quantitative research - see examples listed under word clues
  • measurable
  • numbers 
  • statistics
objective - separate, observes, but doesn't participate 


Hierarchy of study design

This page is designed to give you an understanding of different types of clinical medical studies and how they relate to each other.

Study designs can be thought of as a pyramid. Case reports are the first articles published on new topics so they make up the base of the pyramid. As we progress up the pyramid, the studies become more evidence-based and less numerous. Meta-Analyses are at the top of the pyramid because they can only be written after much other research has been done on a topic. There are many fewer of them but they offer very strong evidence.


Study Design 101 by Himmelfar Health Sciences Library is licensed under BY-NC-ND 3.0

The below links take you to a brief definition of each design along with a real-life example.

Case Report

Cohort Study

Randomized Controlled Trial (RCT)

Systematic Review


Case Report

An article that describes and interprets an individual case, often written in the form of a detailed story. Case reports often describe:

  • Unique cases that cannot be explained by known diseases or syndromes
  • Cases that show an important variation of a disease or condition
  • Cases that show unexpected events that may yield new or useful information
  • Cases in which one patient has two or more unexpected diseases or disorders

Case reports are considered the lowest level of evidence, but they are also the first line of evidence, because they are where new issues and ideas emerge. This is why they form the base of our pyramid. A good case report will be clear about the importance of the observation being reported.

If multiple case reports show something similar, the next step might be a case-control study to determine if there is a relationship between the relevant variables.


  • Can help in the identification of new trends or diseases
  • Can help detect new drug side effects and potential uses (adverse or beneficial)
  • Can help experimenters produce novel hypotheses which can be used for later testing
  • Identifies rare manifestations of a disease


  • Cases may not be generalizable
  • Not based on systematic studies
  • Causes or associations may have other explanations
  • Can be seen as emphasizing the bizarre or focusing on misleading elements


Hymes KB. Cheung T. Greene JB. Prose NS. Marcus A. Ballard H. William DC. Laubenstein LJ. (1981). Kaposi's sarcoma in homosexual men-a report of eight cases. Lancet. 2(8247),598-600.

This case report was published by eight physicians in New York city who had unexpectedly seen eight male patients with Kaposi’s sarcoma (KS). Prior to this, KS was very rare in the U.S. and occurred primarily in the lower extremities of older patients. These cases were decades younger, had generalized KS, and a much lower rate of survival. This was before the discovery of HIV or the use of the term AIDS and this case report was one of the first published items about AIDS patients.               

Cohort Study

A study design where one or more samples (called cohorts) are followed prospectively and subsequent status evaluations with respect to a disease or outcome are conducted to determine which initial participants exposure characteristics (risk factors) are associated with it. As the study is conducted, outcome from participants in each cohort is measured and relationships with specific characteristics determined.


  • Subjects in cohorts can be matched, which limits the influence of confounding variables
  • Standardization of criteria/outcome is possible
  • Easier and cheaper than a randomized controlled trial (RCT)


  • Cohorts can be difficult to identify due to confounding variables
  • No randomization, which means that imbalances in patient characteristics could exist
  • Blinding/masking is difficult
  • Outcome of interest could take time to occur


Lao, X., Liu, X., Deng, H., Chan, T., Ho, K., Wang, F., ... Yeoh, E. (2018). Sleep Quality, Sleep Duration, and the Risk of Coronary Heart Disease: A Prospective Cohort Study With 60,586 AdultsJournal Of Clinical Sleep Medicine, 14(1), 109-117.

This prospective cohort study explored "the joint effects of sleep quality and sleep duration on the development of coronary heart disease." The study included 60,586 participants and an association was shown between increased risk of coronary heart disease and individuals who experienced short sleep duration and poor sleep quality. Long sleep duration did not demonstrate a significant association. 

Randomized Controlled Trial (RCT)

A study design that randomly assigns participants into an experimental group or a control group. As the study is conducted, the only expected difference between the control and experimental groups in a randomized controlled trial (RCT) is the outcome variable being studied.


  • Good randomization will "wash out" any population bias
  • Easier to blind/mask than observational studies
  • Results can be analyzed with well known statistical tools
  • Populations of participating individuals are clearly identified


  • Expensive in terms of time and money
  • Volunteer biases: the population that participates may not be representative of the whole
  • Loss to follow-up attributed to treatment


van Der Horst, N., Smits, D., Petersen, J., Goedhart, E., & Backx, F. (2015). The preventive effect of the nordic hamstring exercise on hamstring injuries in amateur soccer players: a randomized controlled trial. The American Journal of Sports Medicine, 43(6), 1316-1323.

This article reports on the research investigating whether the Nordic Hamstring Exercise is effective in preventing both the incidence and severity of hamstring injuries in male amateur soccer players. Over the course of a year, there was a statistically significant reduction in the incidence of hamstring injuries in players performing the NHE, but for those injured, there was no difference in severity of injury. There was also a high level of compliance in performing the NHE in that group of players.

Systematic Review

A document often written by a panel that provides a comprehensive review of all relevant studies on a particular clinical or health-related topic/question. The systematic review is created after reviewing and combining all the information from both published and unpublished studies (focusing on clinical trials of similar treatments) and then summarizing the findings.


  • Exhaustive review of the current literature and other sources (unpublished studies, ongoing research)
  • Less costly to review prior studies than to create a new study
  • Less time required than conducting a new study
  • Results can be generalized and extrapolated into the general population more broadly than individual studies
  • More reliable and accurate than individual studies
  • Considered an evidence-based resource


  • Very time-consuming
  • May not be easy to combine studies


Parker, H.W. and Vadiveloo, M.K. (2019). Diet quality of vegetarian diets compared with nonvegetarian diets: a systematic review. Nutrition Reviews,

This systematic review was interested in comparing the diet quality of vegetarian and non-vegetarian diets. Twelve studies were included. Vegetarians more closely met recommendations for total fruit, whole grains, seafood and plant protein, and sodium intake. In nine of the twelve studies, vegetarians had higher overall diet quality compared to non-vegetarians. These findings may explain better health outcomes in vegetarians, but additional research is needed to remove any possible confounding variables.


A subset of systematic reviews; a method for systematically combining pertinent qualitative and quantitative study data from several selected studies to develop a single conclusion that has greater statistical power. This conclusion is statistically stronger than the analysis of any single study, due to increased numbers of subjects, greater diversity among subjects, or accumulated effects and results.

Meta-analysis would be used for the following purposes:

  • To establish statistical significance with studies that have conflicting results
  • To develop a more correct estimate of effect magnitude
  • To provide a more complex analysis of harms, safety data, and benefits
  • To examine subgroups with individual numbers that are not statistically significant

If the individual studies utilized randomized controlled trials (RCT), combining several selected RCT results would be the highest-level of evidence on the evidence hierarchy, followed by systematic reviews, which analyze all available studies on a topic.


  • Greater statistical power
  • Confirmatory data analysis
  • Greater ability to extrapolate to general population affected
  • Considered an evidence-based resource


  • Difficult and time consuming to identify appropriate studies
  • Not all studies provide adequate data for inclusion and analysis
  • Requires advanced statistical techniques
  • Heterogeneity of study populations


Nakamura, A., van Der Waerden, J., Melchior, M., Bolze, C., El-Khoury, F., & Pryor, L. (2019). Physical activity during pregnancy and postpartum depression: Systematic review and meta-analysis. Journal of Affective Disorders, 246, 29-41.

This meta-analysis explored whether physical activity during pregnancy prevents postpartum depression. Seventeen studies were included (93,676 women) and analysis showed a "significant reduction in postpartum depression scores in women who were physically active during their pregnancies when compared with inactive women." Possible limitations or moderators of this effect include intensity and frequency of physical activity, type of physical activity, and timepoint in pregnancy (e.g. trimester).


Research sampling

Researchers commonly examine traits or characteristics (parameters) of populations in their studies. A population is a group of individual units with some commonality. For example, a researcher may want to study characteristics of female smokers in the United States. This would be the population being analyzed in the study, but it would be impossible to collect information from all female smokers in the U.S. Therefore, the researcher would select individuals from which to collect the data. This is called sampling. The group from which the data is drawn is a representative sample of the population the results of the study can be generalized to the population as a whole. The image below illustrates process researchers generally go through when conducting sampling.      


Stage one is to define and group the population by applicable characteristics, such as demographics, consumer behavior, geographic location etc.

Stage two is to determine a sampling frame, which is a list of the actual cases from which sample will be drawn. The sampling frame must be representative of the population. 

Stage three is to pick a sampling technique based on the research objectives, parameters and constraints. There are two main types of sampling: probability (random) and non-probability (non-random) sampling. The difference between the two is whether or not the sampling selection involves randomization. Randomization occurs when all members of the sampling frame have an equal opportunity of being selected for the study. See below for commonly used sampling techniques, random and non-random used in clinical research. The below image shows the various types of sampling techniques. 



Stage four is to determine a size that provides relevant data, and avoids sampling errors or biases. Note, too small a sample yields unreliable results, while an overly large sample demands a good deal of time and resources.

Stage five is to execute the sampling process.