Unit 3: Investigative Biology Flashcards
The Scientific Cycle
- observation
- construction of a testable hypothesis
- experimental design
- gathering, recording, and analysis of data
- evaluation of results and conclusions
- the formation of a revised hypothesis where necessary.
What is a null hypothesis
The null hypothesis proposes that there will be no statistically significant effect as a result of the experiment treatment. If there is evidence for an effect, unlikely due to chance, then the null hypothesis is rejected.
Failure to find an effect (a negative result) is a valid finding, as long as…
an experiment is well designed
When can scientific ideas become accepted
once they have been checked independently.
one-off results are treated…
with caution
The importance of publication of methods, data, analysis, and conclusions in scientific reports
so that others are able to repeat an experiment.
Common methods of sharing original scientific findings include
seminars, talks and posters at conferences, and publishing in academic journals.
What is peer review for scientific publication
- Specialists with expertise in the relevant field
- assess the scientific quality of a submitted manuscript and
- make recommendations regarding its suitability for publication.
Why is honesty and integrity important
The replication of experiments by others reduces the opportunity for dishonesty or the deliberate misuse of science.
3Rs
reduce, replace, refine
What risks must be taken into account
The risk to and safety of subject species, individuals, investigators and the environment must be taken into account.
As a result of the risks involved, many areas of scientific research are…
highly regulated and licensed by governments.
Why is legislation important
limits the potential for misuse of studies and data.
When are results reliable
consistent values in repeats and independent replicates.
conditions for validity
variables controlled so that any measured effect is likely to be due to the independent variable.
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.
Pilot studies (4)
- a pilot study is used to help plan procedures, assess validity and check techniques.
- 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
- allows the investigator to establish the number of repeat measurements required to give a representative value for each independent datum point.
What is a multifactoral experiment
A multifactorial experiment involves a combination of more than one independent variable or combination of treatments.
Advantage of experiments in a laboratory
The control of laboratory conditions allows simple experiments to be conducted more easily than in the field.
Disadvantage of experiments in a laboratory
its findings may not be applicable to a wider setting.
Observational studies are good for detecting correlation, but why are they less useful for determining correlation?
Observational studies are good at detecting correlation, but since they do not directly test a hypothesis, they are less useful for determining causation.
What is an observational study
In observational studies the independent variable is not directly controlled by the investigator, for ethical or logistical reasons
What is a confounding variable
other variables besides the independent variable may affect the dependent variable.
Why must confounding variables be kept constant (or at least monitored)
so that their effect on the results can be accounted for in the analysis.
Experimental design to help prevent effects of confounding variables
randomised bloc design
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.
What is placebo effect
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 is in vitro
In vitro refers to the technique of performing a given procedure in a controlled environment outside of a living organism.
examples of in vitro
cells growing in culture medium, proteins in solution, purified organelles.
What is in vivo
refers to experimentation using a whole, living organism
disadvantages of in vivo
- more time consuming
- expensive
Advantages of in vitro
- less expensive
- less time consuming
disadvantages of in vitro
- less precise
-incomplete representation of being able to see effect in whole organism
advantages of in vivo
- more precise
- accurately represents the entire organism as a whole
Where it is impractical to measure every individual, a __________ of the population is selected.
representative sample
What determines the appropriate sample size
The extent of the natural variation within a population.
More variable populations require a larger sample size
A representative sample should share the same…
- mean
- degree of variation
as the population as a whole
What is random sampling
members of the population have an equal chance of being selected.
What is systematic sampling
members of a population are selected at regular intervals.
What is stratified sampling
the population is divided into categories that are then sampled proportionally.
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 the…
precision of the measurement instrument or procedure but not necessarily its accuracy.
Overall results can only be considered reliable if they can be…
achieved consistantly
Overall results can only be considered reliable if they can be…
the data transformation in which numerical values are replaced by their rank when the data are sorted from lowest to highest.
Causation exists if…
the changes in the values of the independent variable are known to cause changes to the value of the dependent variable.
What is selection bias
is the selection of a sample in a non-random way, so that the sample is not representative of the whole population.
Selection bias may have prevented a representative sample being selected.
Ethical requirements of human studies
- confidentiality
- right to withdraw
- informed consent
