Quantitative research Methods Tiny Jaarsma
2018-02-26 2 The scientific method A few specific reflection on quantitative issues Randomization Intervention Blinding Sampling
The scientific method: fundamentals in quantitative methods
Fundamentals of good quantitative research Formulating relevant hypothesis Having a systematic approach the researcher processes logically through steps in a pre- defined plan Adherence to sound methological principles Sample is representative of the population Control minimizing bias, random variation and confounding factors Replication: Repeating observations in your own study
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7 Deduction: top down From the more general to the more specific
8 Induction : bottom up Moving from specific observations to broader generalizations and theories.
Quantitative research Process of inquiry must be objective The researcher must make complete documentation of data and methodology available for careful scrutiny by other scientists and researchers This also allows statistical measures of the reliability of the results to be established Attempt to achieve control over the factors involved in the area of inquiry, which may in turn be manipulated to test new hypotheses in order to gain further knowledge.
Hourglass of research Begin with broad questions Narrow down and focus in on a particular topic Operationalize Measure/Observe Analyze data Reach conclusions Generalize back to questions Publish
The Scientific Method Observation Description Prediction Control Falsifiability Causal explanation
The Scientific Method Observation: variables and measurements Variables: Independent /dependents Controlled Confounding Measurement: - nominal, ordinal, interval, ratio
Variables Aspect of a testing condition that can change or take on different characteristics with different conditions an object, event, idea, feeling, time period, or any other type of category you are trying to measure The independent variables are those that are manipulated to change the dependent variables Dependent: the variable hypothesized to depend on or be caused by another variable
Sodium intake Blood pressure Income Sodium intake
Controlled variable Condition or variable intentionally kept constant throughout the study The purpose is to minimize the effects of the controlled variable on the dependent variables
Confounders A confounding variable is an extra variable that you did not account for and influence both the independent and the dependent variable. They can ruin an experiment and give you useless results
Relationship between icecream sales and number of drownings
Relationship between icecream sales and number of drownings
Other examples? - Relationship between mothers age and infant birthweight - Relationship between the number of storks and children born - Relationship between chocolate eating and happiness???
Confounding is a major threat to the validity of conclusion made about cause and effect, i.e. internal validity, as the observed effects should be attributed to the confounder rather than the independent variable.
The Scientific Method Observation: variables and measurements Variables: Independent /dependents Controlled Confounding Measurement: - nominal, ordinal, ratio
How do we measure? What do you measure in your research?
Measurement scales Nominal / Categorical Ordinal Interval Ratio
Measurement scales Nominal /Categorical Ordinal Interval Ratio
Title/Lecturer 2018-02-26 28 Ordinal Educational experience elementary school graduate high school graduate some college college graduate Interval Annual income $10,000, $15,000 $20,000
The Scientific Method Observation Description Prediction Control Falsifiability Causal explanation
Description Information must be reliable: Replicable/repeatable Valid = relevant to the inquiry
Prediction Hypotheses An educated and testable guess about the answer to your research question Each hypothesis must make a prediction These predictions are then tested, and the hypotheses can either be supported or refuted on the basis of the data
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Falsifiability Falsifiability- elimination of plausible alternatives A gradual process that requires repeated experiments by multiple researchers who must be able to replicate results All hypotheses and theories are in principle subject to disproof There is a point at which there might be a consensus about a particular hypothesis or theory, yet it must in principle remain tentative.
Causality Cause effect (Hume) 1. Strong correlation/relation between cause and effect 2. Cause must precede effect in time 3. Cause is present when effect occurs
Causality (2) Cause effect Necessary Cause is necessary for the effect to occur (the effect cannot occur unless the cause first occurs) Sufficient Requiring no other factors for the effect to occur John Stuart Mill: No alternative explantations
Cause and effect Cause - effect In research: Independent variable dependent variable Smoking cancer? Intelligence income?
Single or multicausal? For example Depression in Heart Failure patients Causes for for non-adherance to therapy
Single or multicausal? For example Depression in Heart Failure patients Medication Symptoms Inflammation
Which design are suitable to proof causality?
Replication Are others able to replicate/repeat your results? A true replicate means a true study of a new member of the population Measuring a characteristic of ONE member of the population many times is not replication (but is important to determine the uncertainty of your method)
Validity Internal validity How confident are we that there was a functional relationship between the dependent variable and the factor(s)? Did the individual change because of what I did/observed, or was the change due to something else? External validity What is the generalizability of the results of a study?
Validity of your study Validity of your instrument