3.2a Experimental skill Flashcards
(23 cards)
What does validity relate to?
Variables that are controlled so that any measured effect is likely to be due to the independent variable.
Variable can be?
continuous or discrete.
What does accuracy relate to?
How close to true value data.
What does reliability relate to?
Confidence in the data and obtaining consistent values in repeats and independent replicates.
What does precision relate to?
How close measured values are to each other.
What is then point in a pilot study?
Used to plan procedures, assess validity and check technique, integral in development of investigation. Allows evaluation and modification.
What is the independent variable?
Changed in scientific experiment
What is the dependent variable?
Being measured.
What is a multifactorial experiment?
More than one independent variable or a combination of treatments.
Observational studies are good at what?
Correlation but do not directly test a hypothesis so less useful for determining causation.
What is not controlled in observational studies?
Independent variable.
What is a randomised block design?
Distributed so influence of any confounding variable is likely to be the same across treatment and control groups.
What are confounding variables?
Other variables that may affect dependent variable. Must be held constant if possible. Or monitored so effect accounted for in analysis.
What is a negative control?
Provides results in the absence of a treatment
What’s a positive control?
Treatment is induced to check system can detect a positive result when it occurs.
What’s a placebo?
Treatment lacking the independent variable being investigated can be induced as a treatment in human trials.
What does in vitro mean?
Technique of performing a given procedure in a controlled environment outside a living organisms.
Advantages - controllable, repeatable, rapid, cheap ethical.
Disadvantages - Chronic effects not tested.
It may be impractical to measure every individual in a population so what is selected?
A representative sample of the population. Should share the same mean and same degree of variation about the mean as the population whole.
What does in vivo mean?
Experiment using a whole living organism.
Advantages - Stimulate real life and chronic effects can be tested .
Disadvantages - difficult ton control, slow, expensive, unethical.
In random sampling members of a population have…
Equal chance of being selected.
In systematic sampling….
Members of a population are selected at regular intervals because an environmental gradient.
In stratified sampling….
Non-homogeneous population divide into categories called strata then sampled proportionally.
Why is a independent replication carried out?
To produce an independent data set.
