Experimental design Flashcards
What is the definition of variable
Any factor that can be controlled, changed or measured in an experiment
What’s a discrete variable
Can have a finite range of values (bar graph)
What’s a continuous variable
Can take on infinitely many uncountable values (line graphs)
What do experiments involve
The manipulation of the independent variable by the investigator
What’s an independent variable
The variable that is changed in a scientific experiment
What’s the dependent variable
The variable that is measured in a scientific experiment
What is a control group compared to
Experimental treatment
What are the two ways experiments are designed
Simple-one independent variable
Multi factorial- more than one independent variable
What is an advantage and disadvantage of simple experiments
Advantage-conducted more easily than in field
Disadvantage- may not be applicable to a wider setting
What’s a multi factorial experiment definition
Experiment involves a combination of more than one independent variable or combination of treatments
Why do investigators use groups that already exist
So there is no truly independent variable
Why is the independent variable not directly controlled in observational studies+ e.g
For ethical or logistical reasons e.g investigating effects of medical conditions
What’s a pro and con of observational studies
Pro- good at detecting correlation
Con- do not a hypothesis so less useful for determining causation
What’s a confounding variable definition
Variables, other than the independent and dependent variables that may affect the results of an investigation and therefore need to be considered during the investigation
When must a confounding variable be held constant or at least monitored
When other variables(confounding)besides the independent variable may effect the dependent variable
What is used when confounding variable cannot easily be controlled
A randomised block design can be used
How are randomised blocks used to influence confounding variables
Influence so the confounding variable is likely to be the same across treatment and control groups
What’s a control definition
An experiment group where no treatment is givin
What are control results used for
Used for comparison with the results of treatment groups
What’s negative control definition
Provides the results in the ABSENCE of treatments e.g iodine stays brown with water
What’s a positive control definition
A treatment that is included to check that the system can detect a positive result when it occurs e.g iodine turns dark blue with startch
What are placebos used for
Can be Included as a treatment without the presence of the independent variable being investigated
What’s the placebo effect
Is a measurable change in the dependent variable as a result of a patient’s expectations rather than changes in the indépendant variable
What is in Vivo definition
Expérimentation using a whole living organism
What is in vitro definition
Performing a given procedure in a controlled environment outside of a living organism
What’s an advantage and disadvantage of in vitro
A-better control of your experiment and any confounding variables
N-not possible for many biological studies. Not representative of whole organism response
What’s an advantage and disadvantage of in vivo
A-better idea of what is going on inside the cell or organism
N-living organisms show great variability which can’t really be controlled
