43O1NATURAL SCIENCE METHODS / NATURVITENSKAPELIGE METODER

Hogskolen iTelemark

EKSAMEN

43O1NATURAL SCIENCE METHODS / NATURVITENSKAPELIGE METODER

24.10.2012

Tid: ^9-12

Milform: BokmilA.,lynorsk/English

Sidetal:

³

Hjelpemiddel: ^Kalkulator

Merknader:

Vedlegg: AbstractavArtikkel: Wenner etal200T.Ducttape forthe treament of common warts in adults. Archiv Dermatol 143, 309-3

13.

Eksamensresultata

blir offentliggiort pi

studentweb.

BOKMAL

EKSAMEN I NATURVITENSKAPELIGE METODER 24.10.2012, kl. 9.00 - 12.00

Alle hovedsparsmdl (1-4) teller like mye, og alle delsporsmdl teller like

mye.

1

.

Noen sentrale grunnbegreper

Forklar disse statistiske

begrepene:

kontinuerlige data bivariate data p-verdi vanans

standard

awik

standard feil konfidensintervall

tilfeldig stratifisert sampling Type I og Type

llfeil

2. Analysemetoder

Hvert Ar har Storbritannia en lkke-royke Dag

pi

andre onsdag i mars. Data ble samlet inn for

A se om antall arbeidsulykker gikk ned ^pA denne ikke-royke dagen. Mange faktorer pAvirker antall arbeidsulykker (f.eks. sesong, ukedag),

si

vi forsoker 6 kontrollere for slike faktorer ved 6 sammenligne med

narmeste

onsdag

for

lkke-royke onsdagen hvert er. Data er

iTabell

1.

Tabell ¹ . Data for arbeidsulykker

i

Storbritannia.

Ar

^{Onsdag for} lkke- lkke-royke royke

Dag

^Dag

1987 516

⁵⁴⁰

1988 610

⁶²⁰

1989 581

⁵⁹⁹

1990 586

⁶³⁹

1991 554

⁶⁰⁷

1992 632

⁶⁰³

1993 479

⁵¹⁹

1994 583

⁵⁶⁰

1995 445

⁵¹⁵

1996 522

⁵⁵⁶

a)

Hvor mange fler eller

farre

arbeidsulykker var det i gjennomsnitt pA lkke+oyke Dag' sammenlignet med en normal arbeidsdag?

b)

Hva er SD for gjennomsnittlige forskjell i antall arbeidsulykker og hva uftrykker dette?

c)

Formel for 6 regne ut 99% konfidensintervall for estimert gjennomsnittlig forskjell ⁱ antall arbeidsulykker er:

(estimert gjennomsnittlig forskjell ⁱ antall arbeidsulykker)

i

^SE " ^to oor, vg.

Her blir f = 3,25 (fra t-tabell). Regn ut 99% konfidensintervall.

d)

Forklar med dine egne ord hva et 99% konfidensintervall betyr.

e)

^Hvilken

^testvil

du bruke for A finne ut om det er forskjell

iantall

arbeidsulykker ^pA lkke-royke Dager?

300

^

b0 ²⁵⁰

J

-

²⁰⁰

(! _1E^

E E -LVU

650 o

0

tei . t.f

tabell 2 deskriptiv statistikk av disse dataene blir presentert.

Tabell 2. Beskrivende statistikk over kroppsmasse av brunbjorn fanget ⁱ to studieomrader ^. Sverige 1989-2010.

Kroppsvekt (i kg)

Mean ^75.1

Standard

enor

1.575205

Median ⁷¹

Standard deviation 50.6521

SamDle variance 2565.635

Kurtosis 1.055054

Skewness '1.040767

Range

282

Minimum 8.0

Maximum 290.0

Sum 77629.7

Sum of souares 8478513

n 1034

a) Er dataene normalfordelt? Forklare hva dine konklusjoner er basert ^pA.

b) Hvilke videre analyser eller tester ville du bruke til A undersske om dataene er normalfordelt eller ikke?

c) Dataene inneholder observasjoner fra voksne hanner, voksne binner, ett ar gamle hanner (= subadulte hanner), og ett er gamle binner (= subadult binner). Hvordan ville du undersske om det er forskjeller i vekt mellom disse kategoriene?

d) Hvordan vil du undersoke (dvs. hvilken type analyse vil du bruke og hvordan ville du sette opp datafilen) om det finnes en signifikant interaksjon mellom alder og kjonn, og om dette interaksjonen pAvirker gjennomsnittlig kroppsvekt av blorn?

4.

Forsoksdesign

og

kritisk

vurdeing

Vedlagt finner du en kopi av Abstract til artikkelen Wenner et al 2007. Duct tape for the treament of common warts in adults. Archiv Dermatol 143, 309-313.'Duct tape' er en type vanlig klar, tjukk tape.

a) Forklar med ord og/eller skisse hva slags forsoksdesign som er brukt.

b) Hvilke sentrale prinsipp for forsoksdesign er oppfylt?

c) Hvilke og hva slags type variable vil resultatene fra forcoket gi?

d) | Abstract er de statistiske testmetoder ikke vist. Hvordan tror du data er analysert for ^A finne ut om duct tape har noen virkning mot vorter?

e) Har du noen forslag til 6 forbedrc forcsksdesignen?

&d-q1

Duct Tape for the Treatment of Common Warts in Adults

A Double -blitrd Rsndonizccl C<nirolkd ^T rial

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ENGLISH

EXAM IN METHODS OF THE NATURAL SCIENCES

24.,,10.20'12.9.00

a.m. - 12.00 a.m.

All main questions (1-4) count equally, and all supplementary questions

have

equal weight.

1. Some important basic concepts

Explain these statistical

concepts:

conlinuous data bivariate data o-value vanance

standard deviation standard error confidence interval

random stratified sampling Type I og Type ll error

2.

Analysis methods

Every year the United Kingdom has a Non-smoking Day on the second Wednesday in March.

Data

were collected to see

if

the number

of

work accidents went down

on

this Non-smoking day. Many factors affect the number

of

work accidents

(e.9.

seasonality, day

of

week), so

it

was tried to control for these factors

by

comparing the nearest Wednesday before Non-smoking Wednesday

in

every year. The data

^are

presented

in

Table

1.

Tabel ¹ . Data for work accidents in the United Kngdom.

Year ^Wednesday

Non-smoking before

Non-

^day

Smoking day

1987 516

⁵⁴⁰

1988 610

⁶²⁰

1989 581

⁵⁹⁹

1990 586

⁶³⁹

1991 554

⁶⁰⁷

1992 632

⁶⁰³

1993 479

⁵¹⁹

1994 583

⁵⁶⁰

1995 445

⁵¹⁵

1996 522

⁵⁵⁶

a)

How many more or fewer work accidents were there on average on the non-smoking day, compared with a normal working day?

b)

What is the SD of the average difference in the number of work accidents and what does it exoresses?

c)

The formula calculating the 99% confidence interval for the estimated mean difference in the number of accidents is::

(estimated mean difference in the number of work accidents)

t

SE.ls.es1.ers.

Here

t=

3,25 (from the t-tabel). Calculate the 99% confidence interval..

Explain in your own words what a 99% confidence interval means.

Which test would you _use to determine whelher there are differences in the number

of

accidents at non-smoking Days?

3.

Analysis methods

In figure 1 you will find data on body mass of brown bears in south-central Sweden. In table ² descriptive statistics of these data are presented.

Figure ¹ . Dotplot of the body mass of live-captured brown bears in two study areas in Sweden from 1989-2010.

300

-.^ l.

ta d) e)

O

i

a a oo o

-a

I

a

t

a

ta

a oolra -t-'

oa

$

^zoo

g

_1so

q

! _o

^roo

50

O o

o

ao

-

^oa

'3..$. 3

aa

f t.

o- a

^o

lo

rf.

tita'

oo

oo o

o

Table 2. DescripfrVe slalrstlcs of the body mass of

brown

bears live-captured in two study areas in Sweden from 1989-2010.

Bodv mass (in kq)

Mean ^75.1

Standard error 1.575205

Median ⁷¹

Standard deviation 50.6521

Sample variance

zcoc.oJc

Kurtosis 1.055054

Skewness 1.040767

Range

282

Minimum 8.0

Maximum 290.0

Sum 77629.7

Sum of souares 8478513

n 1034

a)

Are the data normally distributed? Explain what your conclusions are based on.

b)

Which further analyses or tests would you use to investigate if the data are normally distributed or not?

c)

The data contain observations from adult males, adult females, yearling male (i.e. ^1- year old), and yearling female brown bears. How would you investigate ^if there are differences in body mass between these categories?

d)

^How would you investigate (i.e. which type of analysis would you use and how would you set up the data file) if there is a significant interaction between age and sex and if this interactions affects mean body mass of bears?

4. Experimental design and critical evaluation of experiments

Attached is a copy of the Abstract of the paper Wenner et al. 2007. Duct tape for the treament of common warts in adults. Archiv Dermatol 143, 309-313. 'Duct tape' is a type of thick silver-colored taDe.

a) Explain in words and / or graphically show the kind of experimental design used.

b) Which key principles of experimental design are met?

c) Which and what type of variable will be the results of the experiment shown?

d) The statistical methods are not presented ⁱⁿ the abstract. How do you think the data were analyzed to determine if the duct tape has an effect against warts?

e) Do you have any suggestions to the improve test design?

ld@rAYqL^I

Duct Tape for the Treatment of Common Warts in Adults

A Double-blind Rqndoniztd Ctnlrolled Trial

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