3.2 Experimentation Flashcards
Unit 3: Investigate Biology
What does the term Validity mean?
Variable are controlled so that any measured effect is likely to be due to the independent variable
What does the term Reliability mean?
Consistent values in repeats and independent replicates
What does the term Accuracy mean?
Data, or means of data sets, are close to the true value
What does the term Precision mean?
Measured values are close to each other
Why is a Pilot study completed?
To help plan procedures, assess validity and check techniques
What are 3 advantages of using a pilot study?
-Ensure appropriate range of values for the independent variable
-Allows evaluation and modification of experimental design
-Allows the investigator to establish the number of repeat investigations required to give a representative sample for each dependent data point
What is the difference between a simple experiment and a multifactoral experiment?
A simple experiment has one independent variable, whereas a multifactoral experiment has more than on independent variable or combination of treatments
How can the effect of confounding variables be overcome?
Randomized 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 control groups
What is a Negative Control?
Provides results in the absence of a treatment
What is a Positive Control?
A treatment that is included to check that the system or equipment can detect a positive result when it occurs
What is the Placebo Effect?
This is a measurable change in the dependent variable as a result of a patients expectations, rather than changes in the independent variable
What does In Vitro studies mean?
Preforming a given procedure in a controlled environment outside of a living organism e.g cells growing in culture or proteins in solution
What does In Vivo studies mean?
Experimentation using a whole, living organism e.g a drug trail or environmental sampling
What is an advantage and disadvantage of In Vitro studies?
These can be controlled very tightly, but the findings may not be applicable in a wider setting
What is an advantage and disadvantage of In Vivo studies?
They are more true to life than if the study had been done in the lab, but they are more complex and it is harder to account for the wider range of confounding variables
What is Random Sampling?
Members of the population have an equal chance of being selected e.g closing you eyes and randomly picking
What is Systematic Sampling?
Members of the population are selected at regular intervals e.g 1 in every 5 people
What is Stratified Sampling?
The population is divided into categories that are then sampled proportionally e.g grouped by year corresponding to the number in that year
How can you avoid Selection Bias when sampling?
This is the selection of a sample in a non-random way, so that the sample is not representative of the whole population. Selection bias can be prevented by a representative sample being selected
