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Module 2: Research Design

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Learning Objectives

This module is divided into two sections, Descriptive Studies and Experimental Studies

By the end of this module, you will be able to:

  • Explain how research is designed to gain new knowledge
  • Describe the role(s) of research support staff in enhancing research integrity


RecipeAccording to Trochim (2005), research design "provides the glue that holds the research project together. A design is used to structure the research, to show how all of the major parts of the research project work together to try to address the central research questions." The research design is like a recipe. Just as a recipe provides a list of ingredients and the instructions for preparing a dish, the research design provides the components and the plan for successfully carrying out the study. The research design is the "backbone" of the research protocol.

Research studies are designed in a particular way to increase the chances of collecting the information needed to answer a particular question. The information collected during research is only useful if the research design is sound and follows the research protocol. Carefully following the procedures and techniques outlined in the research protocol will increase the chance that the results of the research will be accurate and meaningful to others. Following the research protocol and thus the design of the study is also important because the results can then be reproduced by other researchers. The more often results are reproduced, the more likely it is that researchers and the public will accept these findings as true. Additionally, the research design must make clear the procedures used to ensure the protection of research subjects, whether human or animal, and to maintain the integrity of the information collected in the study.


HypothesisThere are many ways to design a study to test a hypothesis. The research design that is chosen depends on the type of hypothesis (e.g. Does X cause Y? or How can I describe X and Y? or What is the relationship between X and Y?), how much time and money the study will cost, and whether or not it is possible to find participants. The PI has considered each of these points when designing the study and writing the research protocol.

There are many kinds of research, however, most of them fall into two categories: descriptive and experimental.


Section 1: Descriptive Studies

Definition: A descriptive study is one in which information is collected without changing the environment (i.e., nothing is manipulated).

A descriptive study is one in which information is collected without changing the environment (i.e., nothing is manipulated). Sometimes these are referred to as " correlational " or " observational " studies. The Office of Human Research Protections (OHRP) defines a descriptive study as "Any study that is not truly experimental." In human research, a descriptive study can provide information about the naturally occurring health status, behavior, attitudes or other characteristics of a particular group. Descriptive studies are also conducted to demonstrate associations or relationships between things in the world around you.

Descriptive studies can involve a one-time interaction with groups of people (cross-sectional study),

Cross-sectional study: Group 1, 2 and 3, compared at the same time

or a study might follow individuals over time (longitudinal study).

Longitudinal studyLongitudinal study


Descriptive study Descriptive studies, in which the researcher interacts with the participant, may involve surveys or interviews to collect the necessary information.Descriptive study

Descriptive studies in which the researcher does not interact with the participant include observational studies of people in an environment (e.g., "fly on the wall") and studies involving data collection using existing records (e.g., medical record review).


Case Example For A Descriptive Study

Descriptive Study: Cross-sectional, Longitudinal, Observation, Existing records A researcher wants to know why individuals in Community A have a higher rate of a rare form of cancer when compared to those living in Community B. To find out the reasons for the differences in cancer rates in these two communities, the investigator surveyed residents about their lifestyle, noted the types of businesses that were present in the community and searched medical records. The researcher found that the headquarters for the Toxico Chemical Plant is located in Community A, there is a higher rate of cigarette smoking in this community and residents tended to delay or skip going to the doctor for an annual checkup. In Community B, the largest employer was a department store and on average, residents did not smoke as much as residents from Community A. However, like individuals from Community A, Community B residents tended to delay or skip their annual checkup with their doctor.

Descriptive Study: Awareness ribbons, Toxico chemical plant, Residental area


Section 1: Discussion Questions

  1. What makes this a descriptive study?
  1. Why did the researcher collect information about the lifestyle of community residents? What about the type of businesses present in each community? Medical records?
  1. Can the investigator establish that the chemical plant and cigarette smoking are the cause for the higher rate of cancer among those in Community A?
  1. Can the investigator establish that lower smoking rates and the absence of a chemical factory explains the lower rate of cancer among those in Community B?

Descriptive studies are usually the best methods for collecting information that will demonstrate relationships and describe the world as it exists. These types of studies are often done before an experiment to know what specific things to manipulate and include in an experiment. Bickman and Rog (1998) suggest that descriptive studies can answer questions such as "what is" or "what was." Experiments can typically answer "why" or "how."

Left arrow: Descriptive: What is? What was? Right arrow: Experimental: Why? How?


Section 2: Experimental Studies

Unlike a descriptive study, an experiment is a study in which a treatment, procedure, or program is intentionally introduced and a result or outcome is observed. The American Heritage Dictionary of the English Language defines an experiment as "A test under controlled conditions that is made to demonstrate a known truth, to examine the validity of a hypothesis, or to determine the efficacy of something previously untried."

Manipulation, Control, Random Assignment, Random SelectionTrue experiments have four elements: manipulation, control , random assignment, and random selection. The most important of these elements are manipulation and control. Manipulation means that something is purposefully changed by the researcher in the environment. Control is used to prevent outside factors from influencing the study outcome. When something is manipulated and controlled and then the outcome happens, it makes us more confident that the manipulation "caused" the outcome. In addition, experiments involve highly controlled and systematic procedures in an effort to minimize error and bias, which also increases our confidence that the manipulation "caused" the outcome.


Flipping a coinAnother key element of a true experiment is random assignment. Random assignment means that if there are groups or treatments in the experiment, participants are assigned to these groups or treatments, or randomly (like the flip of a coin).

This means that no matter who the participant is, he/she has an equal chance of getting into all of the groups or treatments in an experiment. This process helps to ensure that the groups or treatments are similar at the beginning of the study so that there is more confidence that the manipulation (group or treatment) "caused" the outcome. More information about random assignment may be found in section Random assignment.

Definition: An experiment is a study in which a treatment, procedure, or program is intentionally introduced and a result or outcome is observed.


Case Example for Experimental Study

Experimental Studies — Example 1

An investigator wants to evaluate whether a new technique to teach math to elementary school students is more effective than the standard teaching method. Using an experimental design, the investigator divides the class randomly (by chance) into two groups and calls them "Group A" and "Group B." The students cannot choose their own group. The random assignment process results in two groups that should share equal characteristics at the beginning of the experiment. TeacherIn Group A, the teacher uses a new teaching method to teach the math lesson. In Group B, the teacher uses a standard teaching method to teach the math lesson. The investigator compares test scores at the end of the semester to evaluate the success of the new teaching method compared to the standard teaching method. At the end of the study, the results indicated that the students in the new teaching method group scored significantly higher on their final exam than the students in the standard teaching group.

Experimental Studies — Example 2

A fitness instructor wants to test the effectiveness of a performance-enhancing herbal supplement on students in her exercise class. To create experimental groups that are similar at the beginning of the study, the students are assigned into two groups at random (they can not choose which group they are in). Students in both groups are given a pill to take every day, but they do not know whether the pill is a placebo (sugar pill) or the herbal supplement. The instructor gives Group A the herbal supplement and Group B receives the placebo (sugar pill). The students' fitness level is compared before and after six weeks of consuming the supplement or the sugar pill. No differences in performance ability were found between the two groups suggesting that the herbal supplement was not effective.


Section 2: Discussion Questions

  1. What makes both of these studies experimental?
  1. What type of information might the investigator collect in these two studies to see if the treatment (e.g. new teaching method or herbal supplement) is effective?
  1. Can the researcher establish cause and effect in either or both of these two studies?
  1. What would happen if the researcher allowed the students to study together or talk about the different methods that were being used to teach the math lesson? Would this be a good or a bad idea? How would this influence the study results?
  1. What if the fitness instructor allowed participants to take other herbal supplements in addition to the supplements being tested? Would this be a good or a bad idea? How would this influence the study results?


Module 2: Quiz Questions

  1. Scenario: You are a Health Educator in a nutrition study that examined the effects of exercise and a low-salt diet on high blood pressure risk reduction. You are responsible for translating the study results and sharing them with local community organizations that may benefit from learning about the study results. The study had significant findings for exercise, but not the low-salt diet. The low-salt diet did not have the expected effect on high blood pressure. However, you really believe in the low-salt diet program and participants in the study really liked the low-salt recipes. What should you do?

    Select the best answer.

    1. Report only the positive effect of exercise because that is all that was found.
    2. Report the positive effect of exercise, but also explain that no effect was found for a low-salt diet.
    3. Report the positive effect of exercise, but also explain the importance of a low-salt diet even though no effect was found for a low-salt diet.
    4. Contact the program manager or PI to explain your worry and ask how it is best for you to proceed.

    See Answer

    b. Report the positive effect of exercise, but also explain that no effect was found for a low-salt diet.

  2. Scenario: At a health clinic, a group of investigators gathered to study the effects of a new medicine in treating a health problem. They designed a Randomized Controlled Trial so that some people would receive the new medicine and others would not. The Institutional Review Board (IRB) reviewed the plan and approved the research study. You are hired as a screening coordinator to recruit participants who meet the eligibility requirements to participate in the study. At the health clinic, you approach a potential participant. You explain the purpose of the study and the eligibility requirements for becoming a participant. He asks, "Why there are so many eligibility requirements for people to participate in the study?" How would you respond?
  3. One of the responsibilities of research personnel is to follow the research protocol.

    1. True
    2. False

    See Answer

    a. True

  4. Why is it important for research staff to maintain the integrity of the research protocol?

    1. To provide a better work environment for the research team
    2. To make the study look more professional
    3. To ensure the study is conducted correctly
    4. To guarantee publication of the study results

    See Answer

    c. To ensure the study is conducted correctly

  5. Why do you need to pay attention to the details outlined in the study protocol?

    1. To learn how to conduct a research study
    2. To follow my responsibilities adequately
    3. To provide information to a participant's family
    4. None of the above

    See Answer

    b. To follow my responsibilities adequately