Practice Laboratory
Part I: Fundamentals of the Scientific Method and the Implementation of Research Agendas1
Melissa Cheyney
Objectives:
1. Introduce the scientific method:
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Generate research questions from observations or literature reviews
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Develop null and active hypotheses based on questions
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Generate prediction statements from hypotheses
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Design experiments to test predictions
2. Apply the scientific method and hypothetical research design to a midwifery care related
question.
A. The Scientific Method.
1. Ask a question:
The starting point in the scientific method is the development of a research question or
questions. A question may be generated through observation of everyday phenomena or through
studying a certain topic in the literature. For example, one current question of obstetrical interest
is why some people suffer high blood pressure during pregnancy and others do not. It has also
been observed that some individuals experience elevated blood pressure with no negative
outcomes while even small increases for others are associated with poorer outcomes. These
relationships also appear to vary for different ethnic groups, socioeconomic statuses, and by parity.
Currently, researchers from a variety of disciplines such as medicine, physiology, nutrition and
anthropology are asking why there is a difference in the incidence of high blood pressure (in its
various forms) in difference samples of U.S. women.
With your preceptors or members of a study group discuss some of the trends in obstetrics and
midwifery care that you have noticed over years or months of observation or have found
interesting from recent readings of the medical and midwifery literature. If you cannot think of
something off hand visit PubMed (http://www.ncbi.nlm.nih.gov/PubMed/) or Medline
(http://intapp.medscape.com/px/medlineapp/medline?cid=med) and read several abstracts from
studies on a topic that interests you. Based on observations and/or a review of the literature on a
topic develop two hypothetical research questions.
Research Question Example: Does spending ten minutes in the hands and knees position twice a
day during the last trimester of pregnancy reduce the number of babies presenting in a posterior
position at the onset of labor as compared to a matched group of pregnant women that do not
spend regular time in the hands and knees position?
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Modified by M. Cheyney for use at the National College of Midwifery from a laboratory exercise on human
biological variation written by M. Cheyney and G. Moreno Black 2003.
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Research Question #1:
Research Question #2:
2. Formulate hypotheses:
Once you have a question, the next step is to try to develop possible answers to the
questions based on research and observations. A possible answer can be framed or stated as a
hypothesis. A hypothesis is an educated guess about the relationship between variables. A
variable is any factor that might change the results of a test or experiment. For example, a few of
the variables in the sample research question above are: maternal position, fetal position, and any
variables used to match experimental and control groups like parity, maternal age etc.
Variables are often categorized into a number of different types depending on such things as
whether their effects can be measured as present or not present or whether they have a wide range
of outcomes and cannot be easily grouped into discrete categories. For example, if we
hypothesized that time spent in hands and knees does influence fetal presentation at the onset of
labor, i.e. anterior or not anterior, then these possible outcomes would be considered discrete
variables because there are a limited number of non-overlapping possibilities. Discrete variables
are also values that are whole numbers (or integers and not fractions) like the number of previous
children or the number of previous miscarriages. You could not have unlimited possibilities of
number of children, for example, because you cannot have fractions of children as in the case of
2.5 children (though 2.5 could be a mean for a sample). If, on the other hand, we hypothesized that
the length of active labor in minutes was dependent on the position of the baby at the outset of
labor, then the length of labor in minutes would be a continuous variable since we could
theoretically have values from several minutes to many, many hours with an infinite number of
possibilities in between that are limited only by our ability to measure them accurately. Variables
which produce a range of values are called continuous variables.
A hypothesis concerning the relationship between variables in question is called an active
hypothesis (Ha). The active hypothesis is an informed idea that is posed or suggested as a
potential answer to a specific question. For example, in the case of the blood pressure example, if
you were trying to understand why some women experience increases in blood pressure during
pregnancy, you might hypothesize that nutritional status or a family history of high blood pressure
plays a role in pregnancy induced hypertension. An active hypothesis based on this might be: the
higher the incidence of family history of hypertension, the more likely a woman is to experience
hypertension during her pregnancy. In an active hypothesis there is a relationship between the
variables.
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An important point concerning the scientific method is that a hypothesis can never be proven true;
rather it is only supported or rejected. For this reason we usually write hypotheses so they can be
rejected. Sometimes researchers will propose that there is no relationship between the variables
under consideration (even though they usually suspect that there is a relationship between
variables). That is, they propose one variable will not have an effect on the other. In this case we
say we are using a null hypothesis (Ho). In the example above, the null hypothesis (Ho) would
state: the incidence of family history of hypertension will have no effect on the rate of pregnancy
induced hypertension.
Think about or discuss the research questions you proposed above and write a null and active
hypothesis for each.
Null Hypothesis #1:
Active Hypothesis #1:
Null Hypothesis #2:
Active Hypothesis #2:
3. Make predictions:
The scientific method uses the null hypothesis (Ho) to make predictions, NOT the active
hypothesis. It is important to recognize that in using the null hypothesis, the prediction is not
based on what you think is going to happen. To generate a prediction from a null hypothesis, place
an “if” in front of the treatment (or independent) variable that is being used in the experiment or
being tested. Then add a “then there will be no effect” before the dependent variable. A
prediction would read: “if we do x then there will be no effect on y”. For example if you were
looking at the relationship between maternal position and fetal presentation you might formulate
an active hypothesis (Ha) that says: “time spent in the hands and knees position daily in the last
trimester is associated with an increase in anteriorly positioned infants.” The null hypothesis (Ho)
would be: “time spent in the hands and knees position daily in the last trimester has no effect on
the position of infants.” A prediction concerning the effect of maternal position on fetal position
would then read: If a woman spends a given amount of time each day in the hands and knees
position, then there will be no effect on fetal position at the onset of active labor.
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Develop a prediction statement for the relationship between the variables you used in your
hypotheses above. Remember you must use the null hypothesis to develop the prediction
statement.
Prediction #1:
Prediction #2:
Ideally, when you conduct an experiment or design a study you try to control for all of the
variables (factors) that may affect the experiment. This is called a controlled experiment. In a
controlled experiment, we assume that the value of one variable, called the dependent variable, is
determined by the value of a second variable, the independent variable. If you switched the
variables around in the statement it would no longer be true, and it probably would not make sense.
For example if you stated that the length of the pushing phase was dependent, in part, on parity
you would say the time of pushing is the dependent variable and parity is the independent variable.
The reverse statement: parity is dependent on the length of pushing does not make sense.
What are the dependent and independent variables in your hypothetical tests?
Hypothesis #1:
Dependent variable Independent variable –
Hypothesis #2:
Dependent variable Independent variable –
4. Test your hypothesis:
In order to test your hypotheses you would have to gather data, input it into a spreadsheet
that can be read by a compatible computer statistical program, and then run specific tests to find
out if there are statistically significant relationships between your variables. In a real life study
numerous variables are often compared using multiple tests. This is what you will be learning
about in the next three sections of this class and also what I recommend you consult a statistician
concerning. Even without knowledge of specific statistical tests you might run, it is helpful to think
about how you would actually design the experiments you have proposed in your hypothetical
studies.
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Write an essay that addresses the following questions:
Design an experiment to test one of your research questions. Explain how you would set it up to
make sure you are gathering accurate data. How would you control for all of the variables in your
study? What are some of the main difficulties in gathering the data you need to answer your
question? Are there biases inherent in your study? If so, how could you correct for these? Is your
research question even possible to address? Is it repeatable? Falsifiable? Are there ethical
ramifications to your work?
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