Experimental design

Question 1

advantages of observational studies

Answer 1

nicht in den natürlichen ablauf der dinge eingreifen

Question 2

disadvantages of observational studies

Answer 2

fast nie kausalitäten erkennen, wirkzusammenhänge erfassen nicht möglich

Question 3

experimental studies

Answer 3

Experimental design is a planned interference in the natural order of events by the researcher.

The importance of experimental design stems from the quest for inference about causes or relationships as opposed to simply description.

advantages-> controlls and repeats

disadvantages-> unrealistic setting

Question 4

The entity

Answer 4

experimentelle einheit

what the treatment is being applied to, should be same as replica

e.g. Petri dish, flask, microcosms, growth chamber, pot

Question 5

The perfect study

Answer 5

Trade-off between experimental control and realism

there is no perfect study

ideally you do everything

Question 6

Replication

Answer 6

number of experimental units per treatment gives replication

Question 7

Experimental controls

Answer 7

often much more work

The control should account for ideally all aspects of the treatment to be examined that are extraneous to the specific treatment, cover all unintentional effects and changes the treatment may have.

Question 8

Randomization of treatments

Answer 8

which experimental unit recieves which treatments must be randomised

position must be randomised

best to keep treatments blind

Question 9

Statistical power

Answer 9

The ability to reject a null hypothesis that is false (finding a true effect) depends on:
• replication (sample size)
• effect size
• alpha level
• variability