Experimentation- Experimental Design

Question 1

What is a variable?

Answer 1

Any factor that can be controlled, changed or measured in an experiment. Variables can be discrete or continuous, independent or dependent

Question 2

What is a continuous variable?

Answer 2

It can take on infinitely many uncomfortable values. For example length, concentration, wavelength

Question 3

What is a discrete variable?

Answer 3

It can have a finite range of values. For example colour, presence/absence

Question 4

During an experiment what variable is manipulated by the investigator?

Answer 4

The independent variable

Question 5

What is an independent variable?

Answer 5

The variable that is changed in a scientific experiment

Question 6

What is a dependent variable?

Answer 6

The variable that is measured in a scientific experiment

Question 7

In an experiment what will an experimental treatment group be compared to?

Answer 7

A control group

Question 8

What are the two ways that experiments be designed?

Answer 8

Either simple or multifactorial

Question 9

What is a simple experiment?

Answer 9

An experiment with one independent variable

Question 10

What is a multifactorial experiment?

Answer 10

An experiment with more than one independent variable or treatment

Question 11

What conditions are better for simple experiments?

Answer 11

The control of laboratory conditions allows simple experiments to be conducted more easily than in the field.

Question 12

What is a drawback of a simple experiment?

Answer 12

Its findings may not be applicable to a wider setting

Question 13

What is an observational study?

Answer 13

Sometimes investigators may use groups that already exist so there is no truly independent variable. In observational studies the independent variable is not directly controlled by the investigator for ethical or logistical reasons

Question 14

What is an example of an observational study?

Answer 14

An observational study is one investigating the relationship between smoking and lung cancer. An experimental group of people who had been smoking for 20 years would be compared with a control group of people who had never smoked. This is the only viable way of recruiting participants as it would be unethical to ask a group of individuals to smoke for 20 years to allow comparison with a control group. Recruiting experimental groups in this way allows researchers to study long term effects of certain variables (e.g. effects lasting decades) which may not otherwise be possible

Question 15

What are observational studies are good at detecting?

Answer 15

Correlation

Question 16

What are observational less useful for determining and why?

Answer 16

They don’t directly test a hypothesis so they are less useful for determining causation

Question 17

What is a confounding variable?

Answer 17

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

Question 18

What must be considered about confounding variables?

Answer 18

Due to the complexities of biological systems other variables besides the independent variable may affect the dependent variable. These cofounding 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

Question 19

When would a random block design be used?

Answer 19

In cases where confounding variables cannot be easily controlled. It is a form of stratified sampling

Question 20

How are randomised blocks of treatment and control groups distributed?

Answer 20

In such a way that the influence of any confounding variable is likely to be the same across the treatment and control groups

Question 21

What is a control?

Answer 21

Experimental treatment groups are often compared with a control group. Control is an experimental group where no treatment is given

Question 22

What are control results used for?

Answer 22

Comparison with the results of treatment groups.

Question 23

What are the two categories of control that can be used?

Answer 23

Negative controls and positive controls

Question 24

What is a negative control?

Answer 24

Provides the results in the absence of treatment

Question 25

What is a positive control?

Answer 25

A treatment that is included to check that the system can detect a positive result when it occurs e.g. ELISA

Question 26

What is a placebo?

Answer 26

A placebo can be included as a treatment without the presence of the independent variable being investigated

Question 27

What is the placebo effect?

Answer 27

It is a measurable change in the dependant variable as a result of a patient’s expectations rather that changes in the independent variable

Question 28

What is in vivo?

Answer 28

Experimentation using a whole living organism. Translating from Latin to ‘in the living’

Question 29

What is in vitro?

Answer 29

Preforming a given procedure in a controlled environment outside of a living organism. Translates from Latin to ‘in the glass’

Question 30

What is an example of in vitro?

Answer 30

Cells growing in culture medium proteins in solution purified organelles

Question 31

What is a advantage of in vitro?

Answer 31

Better control of your experiment and any confounding variables

Question 32

What is a disadvantage of in vitro?

Answer 32

Not possible for many biological studies

Question 33

What is a advantage of in vivo?

Answer 33

You get a better idea of what is going on inside the cell or organism

Question 34

What is a disadvantage of in vivo?

Answer 34

Living organisms show great variability which can’t really be controlled

Question 35

What are clinical trials?

Answer 35

Studies that investigate the effectiveness of new medicines or treatments for humans

Question 36

Why must trials be care fully controlled?

Answer 36

In order to be sure that the observed improvements (for example a medical condition) are due to the test medication and not another factor

Question 37

What is a placebo?

Answer 37

A type of negative control which can be given to human control group on a clinical trial. Typically groups of trial participants will be randomly assigned to either the test or placebo group

Question 38

What is a double blind study design?

Answer 38

When neither the researcher nor the trial participant will know which group they are in until the end of the study. It eliminate bias

Question 39

What is the placebo effect?

Answer 39

It is a measurable change in the dependent variable as a result of a patient’s expectations rather that changes in the independent variable. Which accounts for psychological effects that trial participants may experience purely through the process of being treated