Lab #4 (Kin222) - Lab PDF

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Experiment A

Table A: LVDT Data LVDT (kg)

Known mass (kg)

Corrected Scores (kg)

Trial #1

1.17

1.0

1.05 + 0.0439

Trial #2

1.06

1.0

0.94 + 0.0439

Trial #3

1.14

1.0

1.02 + 0.0439

Trial #4

1.08

1.0

0.96 + 0.0439

Trial #5

1.13

1.0

1.01 + 0.0439

CE

+0.116

VE

+ 0.0439 . Co n s t a n te r r ori swh e name a s u r e ds c o r eh a st h es a mee r r o rf o re a c ht r i a l , a n di s

o f t e nr e f e r r e dt oa sab i a s . Va r i a b l ee r r o ri st hes a meme a s u r e de v e nti sr e pe a t e d wi t hd i ffe r e n tr e s u l t so b t a i n e d , a n di so f t e nr e f e r r e dt oa se x p e r i me n t a lo rr a n d o m e r r o r . 3.Co n s t a n te r r o ro c c ur sb e c a u s eo fe r r o ri nc a l i b r a t i on ,h o we v e rt h i se r r o ri se a s yt o c or r e c ta n do b t a i nt h et r u es c o r e . Va r i a b l ee r r o ri sc a u s e db yi n s t r u me n te r r o ra nd i n t r a i n d i v i d u a le r r o r . Si n c ev a r i a bl ee r r o ri su n p r e d i c t a b l ei tc a n n o tb ec o r r e c t e d a ndt h es c o r e sy o uo b t a i na r en o tt r u es c o r e s . Wh e nc omp l e t i ngme a s u r e me n t s ,i t i si mp o r t a n tt omi n i mi z ev a r i a b l ee r r o rt oa v o i dc on t a mi n a t i o no fs c o r e s . Co n s t a n te r r o ra ffe c t se a c hs c o r et h es a mea n dt h u sd o e sn oti n flu e n c et h e c omp a r i s o nbe t we e nme a s u r e dr e s u l t s . 4.Th i st a r g e td e mo n s t r a t e sl o wc o n s t a n te r r or a n dh i g hv a r i a b l ee r r or . Ac c u r a c yd e fin e st he c o n s t a n tv a r i a b l e , a n dp r e c i s i o nd e fin e st h e v a r i a bl ee r r o r .

Ex p e r i me n tB

Table B: Skinfold data for One Subject Trials Skinfold Thickness (mm) 1 12.0 2 14.2 3 13.8 4 13.6 5 14.0

Mean

13.5 mm

s2Total

0.772 mm

S Total

+ 0.879 mm

s2inst

0.03 mm

s2w/i

0.742 mm

2

2 2

2. Based on the calculations the intra-individual error has a greater influence than instrument error. The intra-individual error accounted for 96.11% of the total variance whereas the instrument error was responsible for only 3.89% of the total variance. This is due to the fact that the instrument was calibrated. A greater percent of intra-individual error may have been due to an inconsistency in the location where the measurements were taken, producing different results and more error. 2

3. A) One step that could be taken to reduce s w/i would be to make sure the person taking the measurement is taking the measurements from the same part of the arm and they are only measuring fat and not muscle. Another step would be to wait long enough between trials to make sure the fat cells return to normal. 2

B) Two steps that could be taken to reduce s inst would be to make sure that the instrument is in working order and ensuring the instrument in calibrated correctly.

Experiment C

Table C: Grip Strength Data for all Subjects Participant ID

Trial 1 (kg)

Trial 2 (kg)

KV LT DM

27 37 26

28 36 27

WL JF

42 56

43 49

LF JP CC

32 58 34

32 65 35

EA LP

32 31

32 32

SL GS PJ

41 62 24

41 60 25

JJ AD

25 30

23 29

VH TG SP

17 55 59

16 58 60

SH SM

30 33

27 32

LO

29

29

2

2

s

174.13 kg

2

188.69 kg

2

2

2. The components of s Total are s b/i ,

s2w/i

2

and s Inst. The variance between

2 individuals, s b/I, refers to the true score variance between different subjects 2

and reliability will increase. The variance within individuals, s w/I, refers to the variance an individual has within their own results and reliability will decrease. 2

The variance with the instruments, s Inst, refers to errors produced by the instruments used in the experiment and will decrease reliability.

Laboratory Three Part A: Measurement Error

Lindsey O'Neill 20471442 Binh Ngo Section 103 February 12, 2014...