Chapter 1 Notes: Process of Science

Learning Objectives

  • Understand how the scientific method is used to test hypotheses.
  • Know the factors that influence the strength of the conclusions of scientific studies.
  • Know the factors that influence whether the results of any given study are applicable to a particular population of humans.
  • Know how to evaluate the evidence in media reports of scientific studies.
  • Know how the scientific process can help us make important decisions about human health.

Definitions & Main Ideas

  • Anecdotal evidence: evidence derived from personal observations and experiences.
  • Non-scientific reasons for discrepancies in reports of scientific studies:
    • miscommunication
    • misrepresentation
    • lack of understanding in the field of study
  • Scientific evidence: evidence derived from systematic and controlled experimentation.
  • Reasons scientific conclusions are modified over time (examples):
    • scientists ask different questions
    • improved technology
    • better evidence
    • experimentation
    • articles reviewed by experts before publishing (peer review)
  • Science:
    • systematic study of the natural world using observations and experiments, with findings often published after peer review.
  • Peer-reviewed: articles reviewed by experts in the field before publication.
  • Hypothesis: an explanation created from prior studies/observations that can be tested (a testable scientific statement).
  • Testable and falsifiable:
    • Testable: a hypothesis can be accepted or rejected based on testing/experimentation.
    • Falsifiable: there exist possible observations that could rule out the hypothesis.
  • Experiment: a controlled, carefully designed test.
  • Experimental group vs. control group:
    • Experimental group: receives the experimental intervention.
    • Control group: receives no experimental intervention (or a standard/placebo treatment).
  • Independent vs. dependent variables:
    • Independent variable: the factor that is intentionally changed/manipulated (in the experimental group).
    • Dependent variable: the outcome measured (the result of the experiment).
  • Example of independent and dependent variables:
    • Independent: water given to a group of plants.
    • Dependent: height of the plants.
    • Note: both variables may be present in control and experimental groups depending on design.
  • Placebo effect:
    • the phenomenon where participants improve or show measured effects after receiving a fake treatment, due to expectation; the control group is given a placebo to mimic the experimental condition.
  • Blind study:
    • Participants do not know which treatment they are receiving.
  • Double-blind study:
    • Neither participants nor researchers know which treatment is being administered.
  • Statistical significance:
    • a mathematical measure of the confidence that results are real and not due to random chance.
    • commonly associated with a confidence level greater than 95%, i.e., ext{confidence} > 0.95 ext{ or } p < 0.05.
  • Ways to strengthen confidence in study results:
    • Replication/repetition by multiple scientists and labs.
    • Larger sample size (more experimental subjects) to increase statistical power and robustness.
    • Consistent findings across independent studies.
  • Personal theory vs. scientific theory:
    • Scientific theory: a hypothesis that continues to be supported after years of testing and evidence; broadly applicable explanations.
    • Personal theory: an individual belief about how things work that may not have been subjected to rigorous testing or broad support.
  • Epidemiology:
    • the study of the distribution and determinants of diseases and health-related patterns in populations; includes identifying risk factors.
  • Correlation:
    • a consistent relationship between two variables, but not necessarily a cause-and-effect relationship (correlation ≠ causation).
  • Factors that may affect a scientific study:
    • Demographic info (ethnicity, sex, age, height, weight)
    • Genetics, diet, health, exercise, environment, substance use/abuse
  • Randomized clinical trials (RCTs):
    • controlled medical experiments in which participants are randomly assigned to receive a treatment or not; often employ blinding to reduce bias.

The Scientific Method: Steps & Core Concepts

  • Five steps of the scientific process/method:
    1. Observe
    2. Hypothesize
    3. Experimentation
    4. Analyze
    5. Conclude
  • Define science-related terms:
    • Science is the systematic pursuit of knowledge about the natural world through observations and experiments, with findings refined through peer review and replication.
    • Hypothesis: a testable explanation or educated guess that can be investigated via experiments and observations.
    • Experiment: a controlled test designed to isolate and measure the effects of an independent variable on a dependent variable.
    • Peer review: critical evaluation by experts before publication to ensure methodological soundness and validity of conclusions.
    • Testability and falsifiability: a theory must be testable with the possibility of being disproven by evidence.
    • Statistical significance: probability that observed effects are not due to chance; commonly associated with a threshold such as p<0.05p < 0.05 or confidence > 0.950.95.

Experimental Design & Validity

  • Experimental vs control groups:
    • Experimental group receives the intervention.
    • Control group does not receive the intervention (or receives a standard treatment/placebo).
  • Independent vs dependent variables:
    • Independent variable is deliberately changed to test its effects.
    • Dependent variable is measured to assess the outcome of the intervention.
  • Placebo effect and blinding:
    • Placebo effect can influence outcomes; placebo controls help isolate treatment effects.
    • Blind study: participants do not know which treatment they receive.
    • Double-blind study: neither participants nor researchers know which treatment is being administered.
  • Testable and falsifiable concepts:
    • A hypothesis must be testable; it must also be falsifiable (there must be observations that could disprove it).

Measurements, Significance, & Confidence

  • Statistical significance:
    • A measure of how likely results are not due to random chance.
    • Common target: confidence > 0.95 or p < 0.05.
  • Repetition and replication:
    • Conducting more experiments and having different scientists replicate findings strengthens confidence.
  • Effects of sample size and subject variability:
    • Larger samples typically yield more reliable estimates and clearer significance signals.

Interpretation, Theory, and Real-World Relevance

  • Epidemiology and correlation:
    • Epidemiology studies disease patterns and risk factors in populations; correlations describe associations, not necessarily causation.
  • When applying findings to populations:
    • Consider demographic and individual factors (ethnicity, sex, age, height, weight), genetics, lifestyle, diet, health status, environment, and substance use.
  • Media reports and evidence:
    • Be cautious of miscommunication or misinterpretation; seek peer-reviewed sources and understand limitations before applying findings to health decisions.

Randomized Clinical Trials (RCTs)

  • Definition and design:
    • A randomized clinical trial is a controlled medical experiment where participants are randomly assigned to receive a treatment or not.
    • Randomization minimizes selection bias and helps establish causal inferences between interventions and outcomes.
  • Common practices:
    • Blinding (single, double) to reduce bias in treatment administration and outcome assessment.

Meta-Notes on the Process

  • The process emphasizes:
    • Systematic observation and testing
    • Distinguishing correlation from causation
    • The importance of replication, sample size, and methodological rigor
    • Critical thinking when evaluating health claims and media reports

Quick Reference Formulas & Key Thresholds

  • Statistical significance threshold: p<0.05p < 0.05 (or confidence >0.95> 0.95)
  • Relationship concept: correlation does not imply causation
  • Replication and power considerations: larger sample sizes increase power to detect true effects

Real-World Implications

  • Understanding these concepts helps in:
    • Evaluating health claims in the media
    • Making informed decisions about personal health based on scientific evidence
    • Recognizing the limits of studies and the role of population applicability