Biology Unit 3 Flashcards
What is the null hypothesis?
the null hypothesis proposes that there will be no statistically significant effect as a result of the experiment treatment
Is failing to find an effect(a negative result) valid?
Yes, as long as an experiment is well designed.
How can conflicting data or conclusions be resolved?
through careful evaluation or can lead to further experimentation
When is the null hypothesis rejected?
when there is evidence for an effect, unlikely due to chance
Scientific ideas only become accepted once….
they have been checked independently
Why are publications of methods, data, analysis, and conclusions in scientific reports important?
so that others are able to repeat the experiment
What are some common methods of sharing new scientific findings?
seminars, talks and posters at conferences, and publishing in academic journals
What is peer review?
Specialists with expertise in the relevant field assess the scientific quality of a submitted manuscript and make recommendations regarding its suitability for publication
What are review articles?
Review articles summarise current knowledge and recent findings in a particular field
Examples of integrity and honesty within science?
unbiased presentation of results, citing and providing references, avoiding plagiarism
What does reduce mean? (animal ethics)
When it is impossible to avoid using animals, use the least number possible without invalidating your results.
What does refine mean? (animal ethics)
trying to refine the procedure to reduce the risk of human error - and therefore reducing the risk of harming the animals
What does replace mean? (animal ethics)
can the animal be replaced with another non-animal alternative?
Name some human ethics principles
informed consent, right to withdraw, confidentiality
What can influence scientific research?
Legislation, regulation, policy and funding
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 accuracy?
data or means of data sets, are close to the true value
What is precision?
measured values are close to eachother
What is a pilot study used to help do?
plan procedures, assess validity, and check techniques
Pilot studies allow evaluation and….
modification of experimental design
The use of a pilot study can ensure an appropriate….
range of values for the independent variable
Pilot studies allow the investigator to establish…
the number of repeat measurements required to give a representative value for each independent datum point
Independent and dependent variables can be…..
continuous or discrete
What is the 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 a simple experimental design?
one independent variable
What is a multifactorial experimental design?
involves a combination of more than one independent variable or combination of treatments
Pro of simple experiments?
The control of laboratory conditions allows simple experiments to be conducted more easily than in the field
Con of simple experiments?
Its findings may not be applicable to a wider setting
Investigators may use groups that already exist, so there is no
truly independent variable
Observational studies are good at detecting
correlation
Since observational studies don’t directly test a hypothesis…
they are less useful for determining causation
What is an observational study?
the independent variable is not directly controlled by the investigator, for ethical or logistical reasons
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
In cases where confounding variables cannot easily be controlled
a randomised block design could be used
What is randomised block design?
randomised blocks of treatment and control groups can be distributed in such a way that the influence of any confounding variable is likely to be the same across the treatment and the control groups
What are control results used for?
comparison with the results of treatment groups
what is a positive control?
A treatment that is included to check that the system can detect a positive result when it occurs
What is a negative control?
the negative control provides results in the absence of treatment
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?
in vitro refers to the technique of performing a given procedure in a controlled environment outside of a living organism
What is in vivo?
In vivo refers to experimentation using a whole, living organism
Examples of in vitro experiments
cells growing in culture medium, proteins in solution, purified organelles
Advantage of in vivo
Allows study of complex interactions. Provides data for effects in whole organisms
Advantage of in vitro
simpler, less expensive, easier to control confounding variables, interpretation of results is simpler
When is a representative sample of the population selected?
Where it is impractical to measure every individual
What determines the appropriate sample size?
The extent of natural variation within a population
More variable populations require a __________ sample size
larger
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 proportionately
Variation in results may be due to
the reliability of measurement methods and/or inherent variation in the specimens . The precision or accuracy of repeated measurements
The natural variation in the biological material being used can be determined by
measuring a sample of individuals from the population
The range of values is a measure of the
extent of variation in the results
Overall results can be only considered reliable if
they can be achieved consistently
What is qualitative data?
subjective and descriptive
What is quantitative data?
Quantitative data can be measured objectively, usually with a numerical value
What is ranked data?
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
Correlation exists if
there is a relationship between two variables
What is correlation?
correlation is an association and does not imply causation
Causastion 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 a positive correlation?
When an increase in one variable is accompanied by an increase in the other variable
What is selection bias?
The selection of a sample in a non-random way, so that the sample is not representative of the whole population
Why is selection bias not good for an experiment?
may prevent a representative sample from being selected
What is a statistically significant result?
one that is unlikely to be due to chance alone
What do error bars indicate?
variability of data around a mean
