Download presentation

Presentation is loading. Please wait.

Published byPaige Vega Modified over 2 years ago

1
Lab K An exercise in experimental design and implementation

2
Between-subjects designWithin-subjects design -each person in the lab would be assigned to one of the four treatments using random allocation (eg. rolling a fair die and ignoring two of the faces, generating random numbers in minitab and ignoring all but digits 1, 2, 3 and 4, etc.) - Randomisation is used so that there are no systematic differences between the people allocated to different treatments – i.e. it attempts to control for potential confounding variables -each person in the lab would be asked to perform the experiment under each of the conditions, i.e. four times - randomization would be used to assign participants to a particular order of the treatments, thereby counterbalancing the design to minimize the potential order-effects acting as a confounding factor

3
Between-subjects designWithin-subjects design Advantages and disadvantages + only requires each participant to do the experiment once, thereby saving time + potential order effects (eg. fatigue, practice, crossover effects) are avoided and do not need to be controlled for in the design + the subsequent analysis is straight forward, as there are four independent groups to compare + the randomization is relatively straight forward - would require a larger number of participants to get adequate numbers in each treatment group Advantages and disadvantages -requires each participant to do the experiment four times, thereby needing a lot of time -introduces potential order effects (eg. fatigue, practice, crossover effects) which the design should carefully consider in order to minimize the potential effects (i.e. lag between experiments) -the subsequent analysis is complex, involving the analysis of repeated measures + more powerful to detect treatment differences, since effects of individuals are controlled + would require a relatively small number of participants to get reliable results for each treatment level

4
Suggested design and why Given our limited numbers in the lab group, we would favour the within-subjects design, notwithstanding the additional work involved in the randomization and the analysis.

5
To make a Latin square… 1.Create a random order of the levels, (e.g. BACD for a four-level IV) 2.Sequentially number the levels in this random order starting with 1. (e.g. B=1, A=2, C=3 and D=4) 3.To create the first order in the Latin square, put the last number/level in the 3rd position, (e.g. 1, 2, 4, 3). If we had more than four levels, N say, then every subsequent unevenly numbered position (e.g. 5, 7, and so on) would have one less than the previous unevenly numbered position as shown in the following table. Order number Level12N3N-14N-25N-36

6
Labeling of the treatment levels in the random order 1 = C 2 = D 3 = B4 = A Latin Square of labels Latin square of treatments 1243Order 1CDAB 2314Order 2DBCA 3421Order 3BADC 4132Order 4ACBD

7
Random allocation to orders

8
Series 1

9
baboon

10
peanut

11
locust

12
carpet

13
glider

14
fleece

15
almond

16
cymbal

17
jackal

18
bikini

19
chisel

20
pepper

21
budgie

22
sandal

23
coyote

24
Series 2

25
badger

26
raisin

27
maggot

28
cooker

29
rocket

30
jacket

31
banana

32
fiddle

33
jaguar

34
blazer

35
hammer

36
potato

37
canary

38
sarong

39
donkey

40
Series 3

41
beaver

42
tomato

43
slater

44
fridge

45
sledge

46
jumper

47
cherry

48
guitar

49
lizard

50
blouse

51
roller

52
radish

53
condor

54
shorts

55
ferret

56
Series 4

57
cougar

58
walnut

59
spider

60
heater

61
sleigh

62
mitten

63
orange

64
violin

65
monkey

66
braces

67
shovel

68
sprout

69
cuckoo

70
slacks

71
gerbil

72

73
Series 1 baboon peanut locust carpet glider fleece almond cymbal jackal bikini chisel pepper budgie sandal coyote

74
Series 2 badger raisin maggot cooker rocket jacket banana fiddle jaguar blazer hammer potato canary sarong donkey

75
Series 3 beaver tomato slater fridge sledge jumper cherry guitar lizard blouse roller radish condor shorts ferret

76
Series 4 cougar walnut spider heater sleigh mitten orange violin monkey braces shovel sprout cuckoo slacks gerbil

77

Similar presentations

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google