Experimentation Flashcards
Validity
Variables controlled so that my measured effect is likely to be due to the independent variable.
Reliability
Consistent values in repeats and independent replicates
Accuracy
Data, or means of data sets, are close to the true value.
Precision
Measured values ne close to each other
What is a pilot study used for?
To help plan procedures, assess validity and check techniques
Simple experiments
One independent variable
Multifactorial experiments
More then one independent variable
Drawback of simple experiments
Its findings may not be applicable to a wider setting
When is there no truly independent variable?
When investigators use groups that already exist.
Drawback of observational studies
Since key do not directly test a hypothesis, they are less useful for determining causation
What happens to the independent variable in observational studies?
It is not directly controlled by the investigator, for ethical or logistical reasons.
Randomised block design
Makes the influence of cry confounding variables likely to be the same across the treatment and control groups.
Negative central
Provides results in the absence of treatment
Positive control
A treatment that is included to check that the system can detect a positive result when it occurs.
Placebos
A treatment without the presence of the independent variable being investigated.
Placebo effect
A measurable change in the dependent variable as a result of a patient’s expectations, rather than changes in the independent variable.
In vitro
Refers to the technique of performing a given procedure in a controlled environment outside of a living organism.
In Viva
Refers to experimentation using a whole, living organism.
When is a representative sample of the population selected?
Where it is impractical to measure every individual
What determines the appropriate sample size?
The extent of the natural variation within a population.
How can a population be representative?
The sample should share the same mean and the same degree of variation about the meant as the population as a whole.
Random sampling
Members of the population have an equal chance of being selected.
Systematic sampling
Members of a population are selected at a regular interval.
Stratified sampling
The population is divided into categories that are then sampled proportionally.
Qualitative data
Subjective and descriptive
Quantitative data
Can be measured objectively, usually with a numerical value.
Ranked data
Numerical values are replaced by their rank when the data are sorted from lowest to highest
When does causation exist?
If the changes in the values of the independent variable are known to cause changes to the value of the dependent variable.
