Lecture 4 Flashcards
Propositional Knowledge
A belief that something is true and in science this is belief should be justified
- science is built on propositional knowledge
- as evidence increases so does the probability that knowledge is true
When to doubt?
- conflicts with other well-founded propositions
- conflicts with common sense
- conflicts with expert opinion
Scientific Inquiry
- approach to increase our knowledge of natural world
- provides us justification for believing something is correct or incorrect
- more scientific inquiry, more evidence, more justification to believe something to be correct or incorrect
Observational Tests
- typically have limited control of other variables
- often faced with “correlation does not equal causation” criticism
- Observational studies of people are not manipulative. This means that variables other than the ones you are interested might account for the results you see
Theoretical Plausibility
It is easier to accept an association as causal when there is a rational and theoretical basis for such a conclusion supported by known biological information
Consistency
Multiple observations of an association (with different test subjects under different circumstances) increase the credibility of a causal finding
Temporality
A cause must precede an effect in time
Strength of Association
The stronger the relationships between the independent variable and the dependent variable, the less likely it is that the relationship is due to an extraneous variable (a cofounder)
Dose-Response Relationship
There should be a direct biological gradient between the independent variable and the dependent variable
Specificity in the Causes
Ideally, the effect has only one cause. In other words, showing that an outcome is best predicted by one primary factor adds credibility to a causal claim
Observational Studies
3 ways this is usually framed
- admit observational tests are a weak (but needed) alternative to controlled experiments
- selecting subjects to make sure potential covariates are accounted for and use care to restrict conclusions
- assess direction and nature of effects of covarying variables rule them out of possible
Observational Tests
- typically have limited control of other variables
- often faced with “correlation does not equal causation” criticism
- change this to “while correlation does not necessarily equal causation, it can result from a causal relationship”
Controlled Experiments
You measure a response variable after manipulating some aspect of your chosen test subjects
A well-designed experiment study manipulates only one variable of interest, holds as many other variables constant, and measures appropriate response variables
Simple and powerful
Biological Variables to Change/Control
- organism age/sex/life-stage
- organism genetics (clonal, population, species differences)
- organism nutrition
- ambient environment (temperature, water, light, atmosphere, etc.)
Controlled Experiments P2
- Most experiments in labs and at small scale
- Allows for lots of control of extraneous variables, repetition of experiment
- More precise measurement of response variable
Experiments
- Manipulates one variable and records response of another
- Tries to control other variables that potentially affect response variable
- Isolates variable of interest and provides very strong support for or against a particular hypothesis
