3.2 Experimentation Flashcards
Define Validity
variables are controlled so that any measured effect is likely due to the independent variable
Define Reliability
consisitant values are achieved in repeats and independent replicates
Define Accuracy
Data or means of data sets are close to the true value
Define Precision
measured values are very close to eachover- this does not necessarily mean they are accurate
What is a pilot study
a smaller scale preliminary study which aim to investigate whether a main larger study is feasible
Why is a pilot study crucial in the development of an investigation
they help to plan procedures, assess validity, and check techniques allowing evaluation and modification of experimental design
What is a variable
any factor which can be controlled, changed or measured during an experiment
What is an independent variable
the variable which is changed in a scientific experiment
What is a dependent variable
variable which is measured in a scientific experiment
What is a simple experiment
an experiment with one independent variable
what is a multifactoral experiment
more than one independent variable or combination of treatments
what is a confounding variable
variables other than the dependent and independent which must be held constant/monitored
How do observational studies work
the independent variable is not directly controlled by the investigator for logistical or ethical reasons
they detect correlation, but not causation
they do not directly test a hypothesis
In cases where confounding variables cannot be controlled what is used
a randomised block design
what does negative control do
provides the results in absense of treatments
what does positive control do
a treatment is included to check that a system can detect a positive result when it occurs
what is the placebo effect
the measurble change in the dependent variable as a result of the patients expectations rather than real changes in the independent variable
what is an in vivo experiment
an experiment using a whole living organism
what is an in vitro experiment
a procedure performed in a controlled environment outside of a living organism
what is an advantage of an in vivo experiment
you get a better idea of what is going on inside the organism/cell
what is a disadvantage of an in vivo experiment
living organisms show great variability and this can not be controlled
what is an advantage of an in vitro experiment
better control of your experiment and any confounding variables
what is a disadvantage of an in vitro experiment
not possible for many biological studies
What is random sampling
members of a population have an equal chance of being selected
what is systematic sampling
members of the population are selected at regular intervals
what is stratified sampling
the population is divided into categories which are then sampled proportionally
