Lesson 7- Experimental Designs (including randomisation, random allocation & standardisation) Flashcards
What is an experimental design?
Experimental Design- how pps are organised within experiment
What are the 3 types of experimental designs?
1) Independent groups
2) Repeated measures
3) Matched pairs
What is the experimental group/treatment?
Experimental treatment/group- ppl exposed to IV e.g. 🍫
What is the control group?
Control group- group receives ✖️ treatment- ✖️ exposed to IV- used as base line level to compare results e.g. group receives ✖️ 🍫
What are the types of control?
1) Randomisation
2) Standardisation
3) Random Allocation
What is randomisation?
Randomisation- use of chance- control effects of bias- decides order of conditions- e.g. random number generator/names in 🧢 - important for repeated measures design as same pps doing 2 different conditions
What is standardisation?
Standardisation- same formalised procedures & instructions for all pps in research study- ⬆️ reliability of study (ability to repeat study & gain same findings)
What is random allocation?
Random allocation- ensures each pps has same chance of being in 1 condition or the other
What is an independent groups design?
Independent Groups Design- different pps used in each of the conditions … each group of pps independent from each another- pps randomly allocated to each condition- balances individual differences (random allocation)
What are the evaluation points of an independent groups design?
Advantages:
1) Order effects ✖️ occur- different pps in each condition- sequence of participation ✖️influence performance/🏃♂- e.g. practice-> better peformance & boredom/tiredness-> worse
2) Chance of demand characteristics ⬇️- pps take part in 1 condition each … ⬇️ chance to guess aim of study which would affect 🏃♂ & data
Disadvantages:
1) ⬆️ pps needed- compared to repeated measures design- 2 experimental conditions (or more) with different pps in each group
2) Individual differences- different pps used in each condition- results … ⬇️ valid- EV involved & has effect on DV- ✖️ just IV- solved using random allocation
What is a repeated measures design?
Repeated Measures design- each pps tested in all conditions of experiment- same pps used
What are the evaluation points of a repeated measures design?
Advantages:
1) ✖️ individual differences- same pps used in all conditions … study ⬆️ valid- only measuring of IV on DV- ✖️ EV
2) Half ⬇️ pps needed- than independent- same pps used in condition 1 & again in condition 2
Disadvantages:
1) Order effects- sequence of tasks affects peformance
- BUT- counterbalancing- avoids order effects- half pps do condition A 1st & then condition B second & 2nd half do condition B 1st & condition A 2nd- changing order of tasks ⬇️ order effects & ⬆️ validity
2) Demand characteristics ⬆️ likely- same pps involved in entire study- ⬆️ likely to guess aim of study & … affects 🏃♂ & data
What is a matched pairs design?
Matched Pairs Design- different pps used in all conditions (like independent groups design) BUT pps matched on characteristics important for study e.g. age, gender, education etc
What are evaluation points of a matched pairs design?
Advantages:
1) ⬇️ risk of order effects- pps take part in 1 condition only (compared to repeated …)
2) Individual differences ⬇️ likely- pps matched on characteristics
Disadvantages:
1) Twice ⬆️ pps needed- compared with repeated …- problematic to locate enough people to take part
2) Difficult & ⏰ consuming- even 2 closely matched pps have different motivation & fatigue at different times- … individual differences ✖️ completely controlled/removed
