3.Experimentation Flashcards
What is accuracy?
data, or means of data, are close to the true value.
What is precise?
measured values are close to each other.
What is validity?
variables controlled so that any measured effect is likely to be due to the independent variable.
What is reliability?
Consistent values in repeats and independent replicates.
what is a pilot study used to?
- Help plan procedures
- Assess validity
- Check techniques
What does a pilot study allow?
Allows evaluation and and modification of experimental design.
What does the pilot study allow?
Allows appropriate range of values for the
independent variable and the investigator to establish the number of repeat measurements required to give a representative value for each independent datum point. - Suitable number of replicates.
What are independent vairables?
The variable that is changed in a scientific experiment.
What are dependent variables?
The variables being measured in a scientific experiment.
What are discrete variables and what method would be used to plot data?
Are distinct and unrelated to each other. Results are displayed by bar graph.
What are continuous variables and what method would be used to plot data?
Have a range of values. Results are displayed using a line graph.
Why are controls used?
As a comparison with treatment groups - Controls show that any effects are the result of the treatment.
What is the purpose of a negative control?
Provides results in the absence of a treatment.
What is the purpose of a positive control?
To check if the system can detect a positive result when it occurs.
What is a placebo?
One group receives a tablet with the drug and the other group receives a tablet without the drug.
What is the placebo effect?
A measurable change in the dependent variable as a result of a patients expectations rather than a change in the independent variable.
What do in vitro investigation consist of?
An investigation carried out in a controlled environment outside of living organisms.
What are examples of in vitro experiments?
- Cells growing in a culture medium
- Proteins in solution
- Purified organelles
What do in vivo investigations consist of?
An investigation carried out using a whole organism (in a living orgainsm)
What do in vivo investigations consist of?
An investigation carried out using a whole organism (in a living organism)
What are the advantages of in vitro experiments?
Confounding variables may be easily controlled.
What are the disadvantages of in vitro experiments?
Its relevance may be limited in in vitro results may not transfer to in vivo.
What are the advantages of in vivo experiments.
Allows researchers to investigate the overall effect of an agent on a living organism.
What are the disadvantages of in vivo experiments?
Many confounding variables difficult to control.
Fieldwork experiments are more applicable to a wider biological setting but there is a lack of control experimental variables.
What should be done if sampling every individual is impractical?
A representative sample of the population is selected.
What determines the appropriate sample size?
The extent of the natural variation within a population.
More variable populations require a larger population size.
What should a representative sample have?
The same mean and the same degree of variation about the mean as the populations as a whole. (Thus preventing selection bias).
What is random sampling?
Random sampling is when members of the population have an equal chance of being selected.
This could be done by pick numbers out of a hat or computer generation.
What is systematic sampling?
Members of a populations are sampled at regular intervals. e.g. line transect.
What is stratified sampling?
The population is divided into categories that are the sampled proportionally.
What may be the reason for variation in experimental results?
- Reliability of measurement methods
- Inherent variation in the specimens
What is precision?
The closeness of repeated measure to each other.
What is accuracy?
The closeness of the measured value to the true value.
How can reliability of measuring instruments or procedures be determined?
Repeated measurements or readings of an individual datum point.
What does variation observed from an investigation indicate?
The precision of the measurement instrument or procedure but not necessarily its accuracy.
What is natural variation?
The natural variation in the biological material being used can be determined by measuring a sample from a population.
What does the range of values measure?
The extent of variation in the results.
If there is a narrow range then the variation is low.
Why should independent replication take place in a pilot study?
To produce independent data sets.
