Unit 3 - 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
What is a pilot study?
Small-scale, preliminary studies which aim to investigate whether crucial components of a main study will be feasible
What is a pilot study used for?
To help plan procedures, assess validity, and check techniques.
What does a pilot study ensure?
An appropriate range of values for the independent variable.
What does a pilot study allow the investigator to do?
Establish the number of repeat measurements required to give representative value for each independent datum point
What is an independent variable?
The variable that is changed in a scientific experiment
What is the dependent variable?
The variable being measured in a scientific experiment
What is the difference between simple and multifactorial experiments?
Simple: One independent variable
Multifactorial: More than one independent variable
What is a drawback of simple experiments?
It’s findings may not be applicable to a wider setting
What is observational studies?
Where the independent variable is not directly controlled by the investigator, for ethical or logistical reasons
What are observational studies good at detecting?
Correlation
Why are observational studies less useful for determining causation?
They don’t directly test a hypothesis
What is a confounding variable?
Variable, other than independent and dependent, that may affect the results of an investigation
Why must confounding variables be held constant if possible?
Their effect on the results can be accounted for in the analysis
What can be used if confounding variables cannot be controlled easily?
A randomised block design
What is a control?
An experimental group where no treatment is given
What are control results used for?
Comparison with results of treatment groups
What does a negative control do?
Provides results in the absence of treatments
What is a positive control group?
A treatment that is included to check that the system can detect a positive result when it occurs
What can placebos be included as?
A treatment without the presence of the independent variable being investigated
What is the placebo effect?
A measurable change in the dependent variable as a result of a patient’s expectations, rather than changes in the independent variable
What is “In Vitro?”
Refers to the technique of performing a given procedure in a controlled environment outside of a living organism
What is “In vivo?”
Refers to experimentation using a whole, living organism
Advantage of “In vitro”
Better control of your experiment and any confounding variables
Disadvantage of “In vitro”
Not possible for many biological studies
Advantage of “In vivo”
Get a better idea of what is going on inside the cell or oganism
Disadvantage of “In vivo”
Living organisms show great variability which cant be controlled
When is a representative sample of a population selected?
Where it is impractical to measure every individual
What should a representative sample share with the whole population?
The same mean and same degree of variation about the mean
What is random sampling?
When members of the population have an equal chance of being selected
What is systematic sampling?
When members of the population are selected at regular intervals
What is stratified sampling?
The population is divided into categories that are then sampled proportionally
What is variation in results due to?
The reliability of measurement methods and/or inherent variation in the specimens
What is variation influenced by?
Precision and accuracy of repeated measurements
How can natural variation in biological material be determined?
Measuring a sample of individuals from the population
When can results be considered reliable?
If they can be achieved consistently
What is qualitative data?
Subjective and descriptive
What is quantitative data?
Can be measured objectively, usually with a numerical value
What is ranked data?
The data transformation in which numerical values are replaced by their rank when the data are sorted from lowest to highest
What do box plots show?
Variation within and between data sets
What are error bars?
Graphical representations of the variability of data and used on graphs to indicate the error or uncertainty in a repeated measurement.
What do large error bars indicate?
High variability
What is correlation?
An association and does not imply causation
When does Causation exist?
If the changes in the values of the independent variable are known to cause change to the value of the dependent variable
When does positive correlation exist?
When an increase in one variable is accompanied by an increase in the other variable
When does negative correlation exist?
When an increase in one variable is accompanied by a decrease in the other variable
