Experimental research design

Question 1

name three key experimental designs

Answer 1

Between-Subjects ; Matched Pair design; Within-subject design

Question 2

Summarise Within-Subject design

Answer 2

One group of participants tested repeteadly (ie each participant experiences each different treatment or different variable, tested on the same outcome).
Reduces variability, but possible carry over effects.

Question 3

Summarise Between-Subject design

Answer 3

Different groups of participants, each group experiences a different treatment or condition of the variable, and are tested on the same outcome.
Simple to implement, no carry over effect but introduces variation as all participants have individual differences

Question 4

Summarise Matched pairs design

Answer 4

Matched pairs design is between subject: participants are grouped together according to relevant variables (age, sex..) each group then experiences a different treatment/condition and tested on the same outcome, aims at reducing variance between groups but time consuming

Question 5

Name four main types of variables

Answer 5

Independent, Dependant, Extraneous, Confounding

Question 6

Describe Dependant variable

Answer 6

Variable that is our outcome and which is influenced by the independent variable in experimental design

Question 7

What is a third variable, unrelated to our experimental question, that might impact our results (influence our DV)

Answer 7

Extraneous variable, it can be individual related such as social class, personality traits, or more general such as time of the day the experiment takes places etc..

Question 8

Confounding variable is

Answer 8

A variable that influences both the DV and IV, causing a spurious association between the two, renders the experiment worthless

Question 9

The variable we manipulate and that the investigator controls is called..

Answer 9

Independent variable

Question 10

What hypothesis are involved in experimental design ?

Answer 10

Experimental hypothesis, what we think will happen, and Null hypothesis on which we base the study, the null hypothesis is always that nothing will happen when we manipulate the IV

Question 11

What are the two types of experimental hypothesis possible?

Answer 11

Uni directional (we predict precisely what we think will happen), or Bi directional (we predict there will be a difference, an effect, but no detail)

Question 12

What is the logic of our Experiment?

Answer 12

Is the experimental data compatible with null hypothesis being true? We don’t explicitly mention the null hypo in our study, we just keep it in mind.

Question 13

What is p value

Answer 13

The probability of our null hypothesis being true - it is always between 0 and 1 - we test wether any difference observed in the data are due to chance, or are significant.

Question 14

P value numerical value is usually

Answer 14

Always between 0 and 1
If P= 0 : no chance at all the results were obtained by chance, our null hypo is false, we reject it
P= 1: results were for sure obtained by chance, we would fail to reject the null hypo
P is almost never 0 or 1 but somewhere in between

Question 15

If our Ho is not true (ie: results diff obtained are unlikely to be due to chance), our P value should be

Answer 15

either lower or equal to 0.05 - We reject the Ho

Question 16

If our Ho is true (ie our results diff are likely to be due to chance), our P value should be

Answer 16

Higher than 0.05 - we fail to reject the Ho

Question 17

When does type 1 error in testing happens

Answer 17

When we reject the null hypothesis, when actually, our results diff were due to chance : False Positive - the lower the p value, the lower the risk of type 1 error

Question 18

Name the 4 levels of data measurements (or scale)

Answer 18

Categorical (Nominal) - Ordinal (order based) - Interval - Ratio level (numerical with meaning)

Question 19

3 examples of ratio level data

Answer 19

Response or reaction time; Age numbers; Grade system in score

Question 20

3 examples of nominal data

Answer 20

eye colour, favourite brand of chocolate, male/female groups

Question 21

How can you minimise nuisance variable in a study (3)

Answer 21

Standardization (holding as many of the variables constant between testing conditions as possible, only manipulating the iV nothing else) - Randomization for between subject design or Counterbalancing for within subject design

Question 22

What is randomization

Answer 22

In a between subject design, we allocate subjects randomly to either group of the experiment, nothing meaningful is used to randomize

Question 23

What is counter balancing

Answer 23

In a within subject design, we split our sample and each group experience each condition in a different order, this can reduce carry over effects