KA 2 Flashcards
What is Validity?
When 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 Accuracy?
When data, or means of data sets, are close to the true value.
What is Precision?
When measured values are close to each other.
What is integral to the development of an investigation?
A pilot study
What is a pilot study used to do?
To help plan procedures, assess validity and check techniques.
What does a pilot study allow for?
This allows evaluation and modification of experimental design
The use of a pilot study can ensure?
An appropriate range of values for the independent variable
In addition a pilot study allows the investigator to?
Establish the number of repeat measurements required to give a representative value for each independent datum point
An independent variable is the variable that is?
Changed in a scientific experiment.
A dependent variable is the variable being?
Measured in a scientific experiment. Independent and dependent variables can be continuous or discrete
Experiments involve the manipulation of the?
Independent variable by the investigator
The experimental treatment group is compared to a?
Control group
The control of laboratory conditions allows for?
Simple experiments to be conducted more easily than in the field.
A drawback of a simple experiment is that?
Its findings may not be applicable to a wider setting.
A multifactorial experiment involves?
A combination of more than one independent variable or combination of treatments.
Investigators may use groups that? What does this mean?
Already exist, so there is no truly independent variable
Observational studies are good at detecting? What are they not useful for?
Correlation, but since they do not directly test a hypothesis, they are less useful for determining causation
In observational studies the independent variable is not? Why?
Directly controlled by the investigator, for ethical or logistical reasons.
Due to the complexities of biological systems what may affect the dependent variable?
Other variables besides the independent variable
Confounding variables must be held… if this isn’t possible what else happens?
Constant if possible, or at least monitored so that their effect on the results can be accounted for in the analysis
In cases where confounding variables cannot easily be controlled, what could be used?
A randomised block design could be used
Randomised blocks of treatment and control groups can be distributed in such a way that the influence of what?
Any confounding variable is likely to be the same across the treatment and control groups.
Control results are used for?
Comparison with the results of treatment groups
The negative control provides results in the?
Absence of a treatment.
A positive control is 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 is 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.
Examples of in vitro experiments include?
Cells growing in culture medium, proteins in solution, purified organelles.
In vivo refers to?
Experimentation using a whole, living organism
Where it is impractical to measure every individual, what sort of sample is selected?
Representative sample of the population is selected
The extent of the natural variation within a population determines?
The appropriate sample size
More variable populations require a larger?
Sample size
A representative sample should share the same…
Mean and the same degree of variation about the mean as the population as a whole
With random sampling members of the population have an equal chance of…
Being selected.
In systematic sampling, members of a population are selected at?
Regular intervals.
In stratified sampling, the population is?
Divided into categories that are then sampled proportionally.
In ecological studies, use… To select?
Random numbers to select quadrats for sampling.
Establish sample size by?
Determining a travelling mean or the cumulative total of species in quadrats.
How can you systematically sample an environment?
By the use of line or belt transects
Use stratified sampling to sample… using a standard formula to calculate the?
Habitats that are not uniform, using a standard formula to calculate the number of samples from each area.
Variation in experimental results may be due to?
The reliability of measurement methods and/or inherent variation in the specimens
The reliability of measuring instruments or procedures can be determined by?
Repeated measurements or readings of an individual datum point.
The variation observed indicates? But not…
The precision of the measurement instrument or procedure but not necessarily its accuracy.
How do you determine the precision of a measuring procedure?
By repeated measurements, and the accuracy of a measuring procedure by calibration against a known standard.
The natural variation in the biological material being used can be determined by?
Measuring a sample of individuals from the population
The mean of repeated measurements will give an?
Indication of the true value being measured
The range of values is a measure of the?
Extent of variation in the results
If there is a narrow range then the…
Variation is low
Independent replication should be carried out to produce?
Independent data sets
Overall results can only be considered reliable if they can be achieved?
Consistently.
Independent data sets should be compared to determine the?
Reliability of the results
Discrete and continuous variables give rise to what kinds of data?
Qualitative, quantitative, or ranked data
What is qualitative data? How can it be measured?
Subjective and descriptive. Quantitative data can be 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.
The type of variable being investigated has consequences for any?
Graphical display or statistical tests that may be used
Correlation exists if there is a?
Relationship between two variables
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 to the value of the dependent variable
A positive correlation exists when?
An increase in one variable is accompanied by an increase in the other variable.
A negative correlation exists when?
An increase in one variable is accompanied by a decrease in the other variable.
Strength of correlation is proportional to?
spread of values from the line of best fit.
