Experimentation Flashcards
What is reliability
Consistent values in repeated and independent replicates.
What is accuracy
Data, or means of data sets, are close to the true value.
What is precision
Measured values are close to each other.
Why is a pilot study used
Integral to the development of an investigation, a pilot study is used to help plan procedures, assess validity, and check techniques.
What do pilot study allow for
This allows evaluation and modification of experimental design.
What can the use of a pilot study ensure
The use of a pilot study can ensure an appropriate range of values for the independent variable.
What can a pilot study allow the investigator to establish
It allows the investigator to establish the number of repeat measurements required to give a representative value for each independent datum point.
What is an independent variable
An independent variable is the variable that is changed in a scientific experiment.
What is a dependent variable
A dependent variable is the variable being measured in a scientific experiment.
Are independent and dependent variables continuous or discrete
Independent and dependent variables can be continuous or discrete.
What variable is manipulated by the investigator
Experiments involve the manipulation of the independent variable by the investigator.
What is the experimental treatment group compared to
The experimental treatment group is compared to the control group.
What is a simple experiment
When there’s one independent variable.
Advantage of a simple experiment
The control of laboratory conditions allows simple experiments to be conducted more easily than in a field.
Disadvantage of a simple experiment
Findings found in laboratory conditions may not be applicable to a wider setting.
What is a multifactorial experiment
When there’s more than one independent variable.
What does a multifactorial experiment involve
A multifactorial experiment involves a combination of more than one independent variable or combinations of treatments.
What is a disadvantage of using groups that already exist
Investigators may use groups that already exist, so there’s no truly independent variable.
What are observational studies good and bad at
Observational studies are good at detecting correlation, but since they do not directly test a hypothesis, they are less useful for determining causation.
Why is the independent variable not directly controlled by the investigator in observational studies
In observational studies, the independent variable is not directly controlled by the investigator for ethical or logistical reasons.
What are confounding variables
When other variables besides the independent variable may affect the dependent variable.
Why must confounding variables be held constant if possible, or at least monitored
Confounding variables must be held constant if possible, or at least monitored so that their effect on the results can be accounted for in the analysis.
What is used when confounding variables cannot be controlled
In cases where confounding variables cannot easily be controlled, a randomised block design could be used.
What are control results compared to
Control results are used for comparison with the results of treatment groups.
What does a negative control provide
The negative control provides results in the absence of treatment.
What is a positive control
A positive control is a treatment that is included to check that the system can detect a positive result when it occurs.
When can placebos be added as a treatment
Placebos can be included as a treatment without the presence of the independent variable being investigated.
What is the placebo effect
The Placebo effect is a measurable change in the dependent variable as a result of a patient’s expectations, rather than changes in the independent variable.
What does in vitro refer to
In vitro refers to the technique of performing a given procedure in a controlled environment outside of a living organism.
What does in vivo refer to
In vivo refers to experimentation using a whole, living organism.
What are the advantages of in vitro
Better control of your experiment and any confounding variables.
What are the disadvantages of in vivo
Not possible for many biological studies.
What are the advantages of in vivo
You get a better idea of what is going on inside the cell or organism.
What are the disadvantages of in vivo
Living organisms show great variability which can’t really be controlled.
When is a representative sample of the population selected
Where it is impractical to measure every individual, a representative sample of the population is selected.
What determines the appropriate sample size
The extent of natural variation within a population determines the appropriate sample size.
What do more variable populations require
More variable populations require a larger sample size.
What should a representative sample share
A representative sample should share the same mean and the same degree of variation about the mean as the population as a whole.
What is random sampling
In random sampling, members of the population have an equal chance of being selected.
What is systematic sampling
In systematic sampling, members of a population are selected at regular intervals.
What is stratified sampling
In stratified sampling, the population is divided into categories that are sampled proportionally.
What is variation caused by
Variation in experimental results may be due to the reliability of measurement methods and/or inherent variation in the specimens.
How can reliability be determined
The reliability of measuring instruments or procedures can be determined by repeated measurements or readings of an individual datum point.
What does variation indicate in an instrument or procedure
The variation observed indicates the precision of the measurement instrument or procedure but not necessarily its accuracy.
How is natural variation determined
The natural variation in the biological material being used can be determined by measuring a sample of individuals from the population.
What gives us an indication of the true value being measured
The mean of these repeated measurements will give an indication of the true value being measured.
What is the range of values a measure of
The range of values is a measure of the extent of variation in the results.
What does it mean if there is a narrow range
If there is a narrow range, then the variation is low.
How is the reliability of the results determined
Independent data sets should be compared to determine the reliability of the results.
What is qualitative data
Qualitative data is subjective and descriptive.
What is quantitative data
Quantitative data can be measured objectively, usually with a numerical value.
What does ranked data refer to
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.
What is correlation
Correlation is an association and does not imply causation. Causation exists if the changes in the values of the independent variable are known to cause changes in the value of the dependent variable.
When does a negative correlation exist
A negative correlation exists when an increase in one variable is accompanied by a decrease in the other variable.
What is a positive correlation
A positive correlation exists when an increase in one variable is accompanied by an increase in the other variable.
