producing data

Question 1

explanatory variables

Answer 1

explain or cause a change in another variable and may be manipulated or have a set value

Question 2

response variable

Answer 2

the measyred variable that changes in response to the explanatory variable

Question 3

confounding variables

Answer 3

thought or known to influence both explanatory and response variables - confuses (known beforehand)

Question 4

lurking variables

Answer 4

like confounding but not known beforehand

Question 5

simpson’s paradox

Answer 5

unfair averaging
better to compare % at each level
overall % can be misleading
arises because of lurking/confounding variables

Question 6

observational experiments

Answer 6

• no manipulation of explanatory variable
• no random assignment
• observe what is happening in natural settings (not contrived)
• causation is difficult to establish
• case-control studies

Question 7

experiments

Answer 7

• manipulation and response
• experimental units (called subjects if human)
• treatments (specific conditions)
• explanatory variables are called factors and have different levels
• factorial experiments look at joint effect of several factors
• placebos and controls
• cause and effect

Question 8

controls

Answer 8

control lurking variables by comparing treatments

• needed for validity
• keep conditions the same between groups
• use placebo and remove placebo effect
• blinding and double blind

Question 9

randomisation

Answer 9

use of impersonal chance to assign experimental units to treatments

• matched pairs but chance is better
• each group has similar background and lurking variables
• random allocation

Question 10

replication

Answer 10

• replicate experiment o many units to reduce chance variation in results
• random error is reduced

Question 11

blocking

Answer 11

• blocking of treatment groups into sub-sections that are similar with respect to confounding variables
• form of control - sort units into blocks (men and women) first and then randomly allocate

Question 12

a standard experiment should be

Answer 12

randomised, controlled, double blind and blocked