3e- Experimental design Flashcards

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1
Q

What is the difference between the independent and dependent variable?

A

Independent variable= the variable that is changed in an experiment
Dependent variable= the variable being measured in an experiment

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2
Q

What can independent and dependent variables be?

A

Discrete or continuous

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3
Q

What do experiments involve?

A

The manipulation of the independent variable by the investigator

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4
Q

What is the experimental group in a experiment compared to?

A

A control group

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5
Q

What is a simple experiement?

A

One where only one independent variable is investigated (e.g. measuring the effect of temperature on enzyme activity)

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6
Q

What is an advantage and a drawback of a simple experiment?

A

Advantage= easy to control conditions of the lab and so allows the experiment to be conducted more easily in the field

Drawback= its findings may not be applicable to a wider setting

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7
Q

What is a multifactorial experiment and what may investigators use in them?

A

Involves a combination of more than one independent variable or combinations of treatments. Investigators may use groups that already exist, so there is truly no one independent variable

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8
Q

What happens in observational studies?

A

The independent variable is not directly controlled by the investigator, for ethical or logistical reasons. Instead they use pre-existing groups to investigate correlation between variables

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9
Q

What are observational studies good for?

A

Detecting correlation but since theydo not directly test a hypothesis, they are less useful for detecting causation

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10
Q

What are confounding variables?

A

Due to the complexities of biological systems, other variables besides the independent variable may affect the dependent variable, these other variables are confounding variables

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11
Q

What must happen to any confounding variables?

A

They must be held constant if possible, or at least monitored so that their effect can be accounted for in analysis

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12
Q

What could be used in experiments where confounding variables cannot be easily controlled?

A

A randomised block design

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13
Q

What is a randomised block design?

A

Blocks of treatments and controls are distributed in such a way that the influence of any confounding variable is likely to be the same across the treatment and control groups

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14
Q

What are control groups used for?

A

Comparison with the results of treatment groups, it is used to prove that it is the independent variable which is the cause of any effect seen in results

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15
Q

What does a negative control do?

A

Provides results in the absence of treatment (e.g. adding a denatured enzyme to substrate when studying the effect of that enzyme on that substrate)

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16
Q

What is a positive control?

A

A treatment that is included to check that the system can detect a positive result when it occurs (e.g. in research into a new asthma treatment , the positive control group would be given an inhale containing medication which has already proved to be effective)

17
Q

What are placebos?

A

They are a treatment without the presence of the independent variable being investigated

18
Q

What is the placebo effect?

A

A measurable change in the dependent variable as a result of the patients expectations, rather than changes in the independent variable

19
Q

What does the term “in vitro” mean?

A

Refers to the technique of performing a given procedure in a controlled environment outside of a living organism

e.g. cells growing in culture medium, proteins in solution

20
Q

What does the term “in vivo” mean?

A

Refers to experimentation using a whole, living organism

21
Q

What are some advantages and disadvantages of “in vitro” studies?

A

Advantages- less expensive
- less time-consuming

Disadvantages- less precise
- incomplete representation of the “in vivo” system

22
Q

What are some advantages and disadvantages of “in vivo” studies?

A

Advantages- more precise
- accurately represent the “in vivo” system

Disadvantages- expensive
- more time-consuming