3.2 - Experimentation Flashcards
Validity
Variables controlled so that any 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 are close to each other
Pilot Study
Used to help plan procedures, assess validity and check techniques
Independent Variable
The variable that is changed in a scientific experiment
Dependent Variable
The variable that is being measured in a scientific experiment
Control Group
Should always be included for comparison to the treatment group
Qualitative Data
Subjective and descriptive
Quantitative Data
Measured objectively usually with a numerical value
Ranked data
Refers to the data transformation in which numerical values are replaced by their rank when the data are sorted from lowest to highest
Simple Experiment
Measuring the effect of one independent variable on a dependent variable
It is easier to conduct and easier to control with respect to laboratory conditions
Multifactorial Experiment
Involves a combination of more than one independent variable or combination of treatments
Observational Studies
Researchers must use groups that already exist- and in this regard no truly independent variable exist
Good at detecting correlation
Less useful for determining causation they do not test a hypothesis
Confounding Variables
- other variables besides the independent variables may affect the dependent variable
- these confounding variables must be held constant or at least monitored so that their effect on the results can be accounted for in analysis
Randomised Block
- Can be used where confounding variables cannot easily be controlled
- Randomised blocks of treatment and control groups can be distributed in such a way that the influence of any confounding variable is likely to be the same across the treatment and control groups
Control Results
- Used for comparison with the results of the treatment groups
- Positive and negative controls may be used
Negative controls
- 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
Can be included as a treatment without the presence of the independent variable being investigated
Placebo Effect
Measurement 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 Vivo
Refers to experimentation using a whole living organism
Advantages of In Vivo
Results translate into a more precise understanding of what happens in a living organism
Advantages of In Vitro
Less time consuming
Less expensive
Disadvantages of In Vivo
More expensive
More time consuming
Disadvantages of In Vitro
Results often do not translate into a precise understanding of what happens in a living organism
Representative Sample
- It is impractical to measure every individual in a population and so a representative sample of the population should be selected
- more variable populations require a larger sample size
Random Sampling
- Members of the population have an equal chance of being selected
- poor representation
- No selection bias
Systematic Sampling
- Members of a population are selected at regular intervals
- More representative sample of the overall population
- Not all members of the population have an equal chance of being selected it can be subjected to selection bias
Stratified Sampling
- The population is divided into categories that are then sampled proportionally
- Highly representative however setting up this form of sampling requires the researcher to know the proportions of each group prior to beginning
