Unit 3

avoiding using animals

using fewer animals

change the way the experiment is carried out so animals suffer as little as possible

small scale investigation of a planned research project used to help • develop and/or practice protocols in order to ensure validity of experimental design • check effectiveness of techniques • find a suitable range of values for the independent variable • identify and control confounding variables • identify suitable numbers of replicates

independant- variable that is changed or controlled dependant- variable that is being tested or measured confounding- any factor that affects dependent variable that isn’t independent- must be held constant or monitored

used in cases where confounding variables can’t easily be controlled, blocks or experimental and control groups can be distributed in such a way that the influence of any confounding variable is likely to be same across all groups

quantitative, qualitative or ranked data

findings may not be applicable to wider setting, control of lab conditions means that these experiments can be conducted more easily than in the field

more than one independant variable

carried out using living organisms, tend to be more complex than in vitro experiments

carried out using biological molecules outwith normal biological system ie. cell culture

studies where there is no independent variable, good at detecting correlation but as they don’t directly test the model, not useful for determining causation

comparison with treatment results

provides results in the absence of a treatment

treatment that is included to check that the system can detect a positive result when it occurs

where it is impractical to measure every individual

extent of natural variation within a population, more variable= larger sample size

same mean and degree of variation about the mean as the population as a whole

members of the population have an equal chance of being selected

members of a population are selected at regular intervals

population is divided into categories that are then sampled proportionally

due to reliability of measurement methods and/or inherent variation in the specimens

by carrying out repeated measurements or readings of an individual data point, the variation observed indicates the precision of the measurement instrument or procedure but not necessarily its accuracy

by measuring a sample of individuals from the population- mean of these repeated measurements will give an indication of the true value being measured