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53-App-Answers.Rmd
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53-App-Answers.Rmd
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# Answers to end-of-chapter exercises {#Answers}
```{r evenAnswers, message=FALSE, warning=FALSE, include=TRUE}
includeEvenAnswers <- FALSE
includeGraphsTables <- FALSE
```
<!-- Define colours as appropriate -->
```{r, child = if (knitr::is_html_output()) {'./children/coloursHTML.Rmd'} else {'./children/coloursLaTeX.Rmd'}}
```
<!-- Since font size reduces, make caption font size smaller -->
`r if( knitr::is_latex_output() ) "\\captionsetup{font=footnotesize}"`
<!-- This Appendix contains answers to *most* (not all) exercises. -->
<!-- Some are fully worked, and some are only brief solutions. -->
<!-- * Answers to Chap.\ \@ref(Intro) (Introduction): Sect.\ \@ref(IntroAnswer). -->
<!-- * Answers to Chap.\ \@ref(RQs) (Research questions): Sect.\ \@ref(RQsAnswer). -->
<!-- * Answers to Chap.\ \@ref(ResearchDesign) (Research design): Sect.\ \@ref(ResearchDesignAnswer). -->
<!-- * Answers to Chap.\ \@ref(Ethics) (Ethics): Sect.\ \@ref(EthicsAnswer). -->
<!-- * Answers to Chap.\ \@ref(Sampling) (Sampling): Sect.\ \@ref(SamplingAnswer). -->
<!-- * Answers to Chap.\ \@ref(FactorsInfluenceY) (Factors that influence the response variable): Sect.\ \@ref(FactorsInfluenceYAnswer). -->
<!-- * Answers to Chap.\ \@ref(DesignExperiment) (Designing experiments): Sect.\ \@ref(DesigningExperimentsAnswer). -->
<!-- * Answers to Chap.\ \@ref(DesignObservational) (Designing observational studies): Sect.\ \@ref(DesigningObservationalAnswer). -->
<!-- * Answers to Chap.\ \@ref(Interpretation) (Interpretation): Sect.\ \@ref(InterpretationAnswer). -->
<!-- * Answers to Chap.\ \@ref(CollectingDataProcedures) (Collecting data): Sect.\ \@ref(CollectionAnswer). -->
<!-- * Answers to Chap.\ \@ref(DescribingVars) (Describing variables): Sect.\ \@ref(DescribeAnswer). -->
<!-- * Answers to Chap.\ \@ref(Graphs) (Graphs): Sect.\ \@ref(GraphsAnswer). -->
<!-- * Answers to Chap.\ \@ref(NumericalQuant) (Numerical summaries for quantitative data): Sect.\ \@ref(NumericalQuantAnswer). -->
<!-- * Answers to Chap.\ \@ref(NumericalQual) (Numerical summaries for qualitative data): Sect.\ \@ref(NumericalQualAnswer). -->
<!-- * Answers to Chap.\ \@ref(MakingDecisions) (Making decisions): Sect.\ \@ref(MakingDecisionsAnswer) -->
<!-- * Answers to Chap.\ \@ref(Probability) (Probability): Sect.\ \@ref(ProbabilityAnswer). -->
<!-- * Answers to Chap.\ \@ref(SamplingDistributions) (Sampling distributions): Sect.\ \@ref(SamplingDistributionsAnswer). -->
<!-- * Answers to Chap.\ \@ref(SamplingVariation) (Sampling variation): Sect.\ \@ref(SamplingVariationExercisesAnswer). -->
<!-- * Answers to Chap.\ \@ref(CIOneProportion) (CIs for one proportion): Sect.\ \@ref(CIOneProportionAnswer). -->
<!-- * Answers to Chap.\ \@ref(AboutCIs) (More about forming CIs): Sect.\ \@ref(AboutCIsAnswer). -->
<!-- * Answers to Chap.\ \@ref(OneMeanConfInterval) (CIs for one mean): Sect.\ \@ref(OneMeanConfIntervalAnswer). -->
<!-- * Answers to Chap.\ \@ref(PairedCI) (CIs for paired data): Sect.\ \@ref(PairedCIExercisesAnswer). -->
<!-- * Answers to Chap.\ \@ref(CITwoMeans) (CIs for two independent means): Sect.\ \@ref(MeansIndSamplesAnswer). -->
<!-- * Answers to Chap.\ \@ref(OddsRatiosCI) (CIs for odds ratios): Sect.\ \@ref(OddsRatiosCIAnswer). -->
<!-- * Answers to Chap.\ \@ref(EstimatingSampleSize) (Sample size estimation): Sect.\ \@ref(EstimatingSampleSizeAnswer) -->
<!-- * Answers to Chap.\ \@ref(TestOneProportion) (Tests for one proportion): Sect.\ \@ref(TestOneProportionAnswer). -->
<!-- * Answers to Chap.\ \@ref(TestOneMean) (Tests for one mean): Sect.\ \@ref(TestOneMeanAnswer). -->
<!-- * Answers to Chap.\ \@ref(MoreAboutTests) (More about hypothesis tests): Sect.\ \@ref(MoreAboutTestsAnswer). -->
<!-- * Answers to Chap.\ \@ref(TestPairedMeans) (Tests for paired mean): Sect.\ \@ref(TestPairedMeansAnswer). -->
<!-- * Answers to Chap.\ \@ref(TestTwoMeans) (Tests for two independent mean): Sect.\ \@ref(TestTwoMeansAnswer). -->
<!-- * Answers to Chap.\ \@ref(TestsOddsRatio) (Tests for odds ratios): Sect.\ \@ref(TestsOddsRatioAnswer). -->
<!-- * Answers to Chap.\ \@ref(TwoQuant) (Relationships between two quantitative variables): Sect.\ \@ref(TwoQuantAnswer). -->
<!-- * Answers to Chap.\ \@ref(Correlation) (Correlation): Sect.\ \@ref(CorrelationAnswer). -->
<!-- * Answers to Chap.\ \@ref(Regression) (Regression): Sect.\ \@ref(RegressionAnswer). -->
<!-- * Answers to Chap.\ \@ref(Reading) (Reading research): Sect.\ \@ref(ReadAnswer). -->
<!-- * Answers to Chap.\ \@ref(WritingResearch) (Writing research): Sect.\ \@ref(WriteAnswer). -->
### Chap.\ \@ref(Intro): Introduction {.unlisted .unnumbered}
:::::: {.ChapAnswers data-latex=""}
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsTypeTourniquet).**
**Quant**itative.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsTypeMangroves).**
**Qual**itative.
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsTypeSideEffects).**
**Quant**itative.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsTypeSolarPanels).**
**Quant**itative.
:::
`r if( !includeEvenAnswers) "-->"`
::::::
### Chap.\ \@ref(RQs): RQs {.unlisted .unnumbered}
:::::: {.ChapAnswers data-latex=""}
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsOutcomeResponse1).**
**1.** *Percentage* of vehicles that crash.
**2.** *Average* jump height.
**3.** *Average* number of tomatoes per plant.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsOutcomeResponse2).**
**1.** *Percentage* people who owns a car.
**2.** *Average* time for seedlings to sprout.
**3.** *Average* amount of caffeine in soft drinks.
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsComparisonExplanatory1).**
**1.** Type of diet.
**2.** Whether coffee is caffeinated or decaffeinated.
**3.** Number iron tablets per day.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsComparisonExplanatory2).**
**1.** Whether the vegetables frozen or fresh.
**2.** Type of fuel.
**3.** Size of city.
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsComparisonVsPaired1).**
**1.** *Between*-individuals.
Outcome: percentage wearing hats.
**2.** *Between*-intervals.
Outcome: average yield (in kg/plant, tomatoes/plant, etc).
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsComparisonVsPaired2).**
**1.** *Within*-individuals.
Outcome: average balance times.
**2.** *Within*-individuals comparison.
Outcome: average cholesterol levels.
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsDogs).**
**1.** Correlational.
**2.** No sense assigning one variable as explanatory, another response.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsTypingCor).**
**1.** Correlational.
**2.** Age probably impacts typing speed; age: explanatory; typing speed: response
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsBloodPressure).**
**1.** P: Danish University students; O: *Average* resting diastolic blood pressure; C: between students who regularly drive, ride their bicycles to uni.
**2.** No intervention.
**3.** Relational.
**4.** Decision-making.
**5.** *Conceptual*: 'regularly'; 'university student' (on-campus? undergraduate? full-time?). *Operational*: how 'resting diastolic blood pressure' measured.
**6.** Resting diastolic blood pressure; whether they regularly drive, ride to uni.
**7.** Danish university students; Danish university students.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsNutrition).**
**1.** Some elements not well defined; perhaps: P: Children aged under\ $3$ in a Peruvian peri-urban community; O: proportion of children with diarrhoea; C: nutritional status; no intervention.
**2.** Perhaps: 'In children aged under\ $3$ in a Peruvian peri-urban community, is there a relationship between diarrhoea status and nutritional status?'.
**3.** 'Nutritional status' not well defined. Perhaps amount intake per day? Then, correlational probably.
**4.** Decision-making.
**5.** 'Diarrhea status'; 'nutritional status'; probably others.
**6.** Response: diarrhoea status; explanatory: nutritional status.
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsWalkingSpeed).**
**1.** Probably relational.
**2.** Two-tailed.
**3.** Probably not.
**4.** How *individual* people using phones ('Talking'; 'texting').
**5.** Walking speed.
**6.** *Average* walking speed.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsAnimals).**
**1.** Animal.
**2.** *Pen*: food is allocated to pen.
Animals in the same pen are not independent: they compete for the same space, food, resources, and have similar environments.
**3.** Between diets.
:::
`r if( !includeEvenAnswers) "-->"`
<!-- SEM 2 2018: Christopher WALTON; WILLIUAM LUDOWYK; LOK RAJ BHATTA-->
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:ProjectRQ2).**
The $10$ adults is sample.
Unclear how many fonts compared (or which fonts).
Perhaps: 'Among Australian adults, is the average time taken to read a passage of text different when Arial font is used compared to Times Roman font?'
:::
<!-- SEM 2 2018: Alex Bruce; Levi Crawley; Stuart Stevens-->
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:ProjectRQ3).**
Outcome should be *average* lung capacity.
Perhaps: 'For students that study at (University), Sippy Downs, do males have a larger *average* lung capacity than females?'
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsCommonCold).**
**1.** Japanese adults.
**2.** Between those who take and do not take Vitamin\ C tablets.
**3.** *Average* cold duration'.
**4.** Duration of cold symptoms for each person.
**5.** Whether or not each person takes Vitamin\ C tablets or not.
**6.** Decision-making
**7.** One-tailed.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsBlueGum).**
False.
True.
True.
Sample size: $20$.
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsNoseHair).**
**1.** Analysis: person; observation: individual nose hairs.
Each unit of analysis has $50$ units of observation.
**2.** $n = 2$.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsenvironments).**
**1.** Between environments.
**2.** *Before* and *after* for each individual.
**3.** Operational.
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:POCIaccelerometer).**
**1.** P: American adults; individuals: American adults.
**2.** O: average number of recorded steps.
**3.** Response: number of steps recorded for individuals.
Explanatory: location of accelerometer.
**4.** *Within* individuals.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsTypesZinc).**
**1.** Descriptive; estimation.
**2.** Descriptive; decision-making.
**3.** Correlational; estimation.
**4.** Relational; decision-making.
Unclear if intervention; seems unlikely.
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:RQsComparisonConnectionCaloric).**
**1.** Relational; decision-making.
**2.** Correlational; estimation.
Unclear if intervention; seems unlikely.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:InterventionalRQWithin).**
**1.** Relational; estimation.
**2.** Relational; decision-making.
Intervention (whether worms were used or not).
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:UnitsAnalysis).**
Unit of observation: tyre.
Unit of analysis: car.
Brand allocated to car; each car gets only the same brand of tyre.
Tyres on one car exposed to the same day-to-day use, drivers, distances, conditions, etc.
Each unit of analysis (car) produces four units of observations.
*Sample size*: $10$ cars ($40$ observations).
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:UnitsAnalysis2).**
Analysis: $12$ subjects.
Observation: $6$ per subjects: $72$.
:::
`r if( !includeEvenAnswers) "-->"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:UnitsAnalysisBamboo).**
The board.
Five units of analysis.
Ten.
Ten.
Within-board variation much smaller (apart from first board).
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:PoorRQs).**
**1.** Should be worded terms of averages or means.
**2.** Everyone dies; a time-frame is probably meant (i.e., within twelve months after amputation).
And compared to what?
**3.** No defined population (frozen beans? fresh butter beans? tinned kidney beans? jelly beans? coffee beans? can sizes?); "amount" of salt should be, for example, the "average" amount (or concentration) of salt, and per
100\ g or similar.
Anyway: You can look at the label (unless, of course, you wish to query those values).
**4.** Silly: elephants are huge, and joeys are tiny; no-one needs to test this.
Also,the RQ talks about "weight" rather than 'mean weight' too.
**5.** Needs to be more specific! Perhaps: 'Is the mean reaction time different for males and females?' or similar.
:::
`r if( !includeEvenAnswers) "-->"`
::::::
### Chap.\ \@ref(FactorsInfluenceY): Overview of research design {.unlisted .unnumbered}
:::::: {.ChapAnswers data-latex=""}
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:MineArsenic).**
**1.** Arsenic concentration.
**2.** Distance of lake from mine.
**3.** No: recorded; cannot be lurking.
**4.** Yes: may be related to the response, explanatory variables.
**5.** Confounding variable.
**6.** Observational: researchers do not determine the distance of lakes from mine.
:::
`r if( !includeEvenAnswers) "<!--"`
::: {.answer data-latex=""}
**Ex.\ \@ref(exr:FactorsInfluenceYStudy1).**
*Response*: depression.
*Explanatory*: diet quality.
*Extraneous*: presumably *all* listed as that is why the researchers obtained this information.
*None* can be lurking variables: researchers measure or observe them.
*Confounding* variable potentially related to *both* the response *and* explanatory variables.
Hence, all of the extraneous variables could potentially be confounding variables.
:::
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**Ex.\ \@ref(exr:FactorsInfluenceYStudy2).**
*Response*: perhaps 'risk of developing a cancer of the digestive system'.
*Explanatory*: 'whether or not the participants drank green tea at least three times a week'.
*Lurking*: 'health consciousness of the participants' (appears unrecorded).
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**Ex.\ \@ref(exr:FactorsInfluenceYStudy3).**
Older children more likely to be smokers, and would be larger in general: age is a confounding variable.
Age is easy to record, and usually *is* recorded in these types of studies, so probably *not* a lurking variable.
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### Chap.\ \@ref(ResearchDesign): Types of study designs {.unlisted .unnumbered}
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**Ex.\ \@ref(exr:TypesOfDesignsAcuteOtitis).**
**1.** Between-individuals.
**2.** Relational.
**3.** Most likely.
**4.** Estimation.
**5.** Intervention, so experiment.
Likely true experiment.
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**Ex.\ \@ref(exr:TypesOfDesignsWorms).**
**1.** Between-individuals.
**2.** Relational if the C is between individuals.
**3.** Yes.
**4.** Decision-making.
**5.** Experimental. True experiment.
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**Ex.\ \@ref(exr:ResearchDesignConcreteBeams).**
*True experiment*.
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**Ex.\ \@ref(exr:ResearchDesignVAP).**
**1.** Relational.
**2.** Between-individuals if it is relational.
**3.** Yes, since the program were imposed.
**4.** Experimental.
Program given to paramedics in certain cities; quasi-experimental (researchers cannot tell paramedics where to work).
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**Ex.\ \@ref(exr:ResearchDesignMatresses).**
*Quasi-experiment*.
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**Ex.\ \@ref(exr:ResearchDesignPetsAndHealth).**
**1.** Many answers possible.
**2.** Researchers need to *intervene*: to *give* or *not give* subjects a pet.
**3.** Researchers need to *not* intervene: find the subjects who *already* own a pet, or who did not *already* own a pet.
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**Ex.\ \@ref(exr:ResearchDesignDietsForWeightLoss).**
**1.** Diet.
**2.** Change in body weight after $2$\ years.
**3.** Experimental: diets *manipulated* and *imposed* by the researchers.
**4.** Probably true experiment.
**5.** Individuals: diets allocated to individuals.
**6.** Individuals: those from whom the weight change is taken.
**7.** *Change* in body weight over two years.
**8.** Type of diet.
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### Chap.\ \@ref(Ethics): Ethics {.unlisted .unnumbered}
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**Ex.\ \@ref(exr:EthicsCougars).**
Answers vary.
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**Ex.\ \@ref(exr:EthicsLying).**
Answers vary.
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**Ex.\ \@ref(exr:EthicsSideEffects).**
Answers vary.
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**Ex.\ \@ref(exr:EthicsLying).**
Answers vary.
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### Chap.\ \@ref(Sampling): Sampling {.unlisted .unnumbered}
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**Ex.\ \@ref(exr:SamplingAdvantageRandom).**
c. Externally-valid study more likely.
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**Ex.\ \@ref(exr:SamplingAdvantageLarge).**
d. Precise estimates more likely.
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**Ex.\ \@ref(exr:SamplingSystematicProblem).**
**1.** Every $7$th day is same day of week.
**2.** Maybe select days at random over three-months.
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**Ex.\ \@ref(exr:SamplingBooks).**
Remember: some books borrowed, and not physically in the library!
**1.** Simple random sample:
list of all the books held by the library is needed.
*May* be possible, but probably not for a student or non-library staff member.
In principle: number each book, randomly select a sample from that list.
**2.** Stratified:
campuses as strata; a random sample of all the book in each location.
**3.** Cluster:
each shelf as a cluster; randomly select some shelves; determine the number of pages in each book on the selected shelves.
**4.** Convenience:
finding books in the libraries easily accessible.
**5.** Multi-stage:
random sample of campuses; random sample of shelves in the selected libraries; random shelf from each one; a small number of random book from each shelf.
**6.** Multi-stage perhaps...?
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**Ex.\ \@ref(exr:SamplingApartments).**
**1.** Multi-stage.
**2.** Stratified (selecting floor), then convenience.
**3.** Convenience.
**4.** Part stratified (selecting floors), then convenience.
First might be best.
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**Ex.\ \@ref(exr:SamplingShoppingCentre).**
**1.** Convenience; approaching every $10$th person may make it a little more representative.
**2.** Convenience; by approaching every $5$th person and going *every day* for a week, trying to make it a little more representative (and better than the first)
**3.** Self-selecting.
**4.** Convenience.
By going every day for two weeks, at different times and locations each week, and approaching someone every $15$\ mins, the sample more representative.
The fourth is best, but still far from 'random'.
None truly random.
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**Ex.\ \@ref(exr:SamplingSchools).**
Random sampling to select schools.
Then, self-selecting.
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**Ex.\ \@ref(exr:SamplingMalaria).**
True; False; True.
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**Ex.\ \@ref(exr:SamplingForest).**
Stratified: zones are strata.
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**Ex.\ \@ref(exr:BiasOnline).**
No answer (yet).
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**Ex.\ \@ref(exr:NotMultistageSampling).**
In Stage\ $2$, selection of farms *not* random.
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**Ex.\ \@ref(exr:NotClusterSampling).**
In Stage\ $1$, selection of schools *not* random.
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**Ex.\ \@ref(exr:SolarSampling).**
**1.** Households in Santiago.
**2.** ...if the sample is representative of all households in Santiago.
**3.** Voluntary response.
**4.**Multi-stage.
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### Chap.\ \@ref(DesignInternal): Internal validity {.unlisted .unnumbered}
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**Ex.\ \@ref(exr:DesignTrueFalse).**
All are false.
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**Ex.\ \@ref(exr:DesignTrueFalse2).**
False; true; false; false; true.
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**Ex.\ \@ref(exr:DesignExpImproveIV).**
Yes; yes; yes; yes; yes; no (*external* validity).
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**Ex.\ \@ref(exr:DesignExpImproveIV).**
Yes; yes; yes; **no**; yes; no (*external* validity).
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**Ex.\ \@ref(exr:ResearchDesignObsPollen).**
Probably in case hive size is a confounder.
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**Ex.\ \@ref(exr:DesignExpExtraneous).**
Lurking; confounding.
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**Ex.\ \@ref(exr:DesignExpWeightLoss).**
Statements\ 1, 3, 4, 8 and\ 9 true.
'Sex', 'Initial weight' possible confounders.
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**Ex.\ \@ref(exr:ResearchSmokingAlfresco).**
**1.**. Observational.
**2.** PM~$2.5$~ concentration; number of smokers.
**3.** Possibly: wind speed; amount of cover.
**4.** Yes: be discreet.
**5.** No.
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**Ex.\ \@ref(exr:ResearchDesignSunscreen).**
**1.** Observational.
**2.** *Response*: amount of sunscreen used; *explanatory*: time applying sunscreen.
**3.** Potential confounding variables.
**4.** If the mean of both the response and explanatory variables was different for females and males, sex of the participant a *confounder*; would need to be factored into the data analysis.
**5.** Participants blinded to what is happening in study.
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**Ex.\ \@ref(exr:DesignExpParamedicsPills).**
**1.** Experimental.
**2.** A group receiving a pill like Treatment\ A and\ B, with no effective ingredient.
**3.** Blinding participants.
**4.** To ensure participants do not change behaviour because of the treatment received.
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**Ex.\ \@ref(exr:ResearchTasteOfWater2).**
**1.** Randomly allocate type of water to subjects (or the *order* subjects taste *each* drink.)
**2.** Subjects do not know which type of water they are drinking.
**3.** Person providing water and receiving ratings does not know which type of water subjects drinking.
**4.** Hard to find a control.
**5.** Any random sampling is good, if possible.
Observer effect: researcher directly contacting the subjects; may unintentionally influence responses.
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**Ex.\ \@ref(exr:ResearchDesignTasteOfWater).**
*Random allocation*: not possible (observational).
*Blinding*: students unaware of which water they drink; in observational study, probably infeasible.
*Double blinding*: neither students nor researchers know which type of water students are drinking; probably infeasible.
*Control*: not sensible.
*Random sample*: any random sampling method preferred; possible, but unlikely.
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**Ex.\ \@ref(exr:ResearchDesignFertilizer).**
Carry-over effect; observer effect.
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**Ex.\ \@ref(exr:ResearchDesignDust).**
**1.** Random allocation; blocking; recording potential confounders.
**2.** Blinding participants, researchers.
**3.** Change in nasal congestion.
**4.** Type of cleaning.
**5.** Age; sex.
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**Ex.\ \@ref(exr:ResearchDesignHawthorneEffect).**
No; also possible in observational studies.
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### Chap.\ \@ref(Interpretation): Research design limitations {.unlisted .unnumbered}
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**Ex.\ \@ref(exr:ValidityLighting).**
External.
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**Ex.\ \@ref(exr:InterpretationExerciseValidities).**
Ecological; external; internal; confounding; sampling.
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**Ex.\ \@ref(exr:InterpretationExerciseExternalValidity).**
Population: 'on-campus university students where (I) work'.
External validity: whether the results apply to other members of *target population*.
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**Ex.\ \@ref(exr:InterpretationExerciseParachutes).**
Not *ecologically valid* (e.g., parachutes used at high altitude).
Probably not *externally valid*: voluntary (and presumably convenience) sample.
*Internal validity* may be fine...
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**Ex.\ \@ref(exr:InterpretationSleep).**
Sample not random; the researchers (rightly) state that results may not *generalise* to all hospitals.
Because data only collected at night, perhaps not *ecologically valid*.
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**Ex.\ \@ref(exr:LimitationsShopping).**
Internal.
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**Ex.\ \@ref(exr:CoughDrops).**
Observational study: people with severe cough may take more cough drops.
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**Ex.\ \@ref(exr:StatementsWithErrors).**
**1.** Study is observational because the researchers cannot determine the *comparison* (not the outcome).
**2.** This is a mix of both C ('smokers and non-smokers') and O ('the median serum cholesterol').
**3.** External validity only refers to whether the sample represents the given target population, which is Australians. Whether the results apply for the entire world is irrelevant.
**4.** 'Serum cholesterol' is not a variable; nothing here is varying.
'Serum cholesterol' is just a type of cholesterol.
The variable is 'the serum cholesterol concentration' or similar.
**5.** This is not an experiment.
**6.** The data file will have two columns (variables), but one column will record the smoking status (Yes/No) and one column will record the serum cholesterol concentration.
**7.** A confounding variable has to be related to both the response and explanatory variables.
**8.** The observer effect is about how the researchers might respond, not the individuals under study.
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**Ex.\ \@ref(exr:ResearchDesignSleep).**
Patients probably knew they were involved; Hawthorne effect should be considered in interpretation.
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**Ex.\ \@ref(exr:ValidityBeer).**
Study lacks *ecological validity*.
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### Chap.\ \@ref(CollectingDataProcedures): Collecting data {.unlisted .unnumbered}
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**Ex.\ \@ref(exr:CollectSurveyQuestions1).**
No place for $18$-year-olds.
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**Ex.\ \@ref(exr:CollectSurveyQuestions1B).**
'$2$ children' belong in two categories (not mutually exclusive); '$4$ children' does not belong in any category (not exhaustive).
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**Ex.\ \@ref(exr:CollectSurveyQuestions2).**
Best: second.
First: *leading* (*concerned* cat owners...)
Third: *leading* (Do you *agree*...)
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**Ex.\ \@ref(exr:CollectSurveyQuestions2B).**
First: *leading* ('environmentally friendly').
First and second: only present the option of 'owning'
Third: best question.
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**Ex.\ \@ref(exr:SunscreenQuestions)**.
First fine; 'seldom' (for instance) may mean different things to different people; possible recall bias.
Second: overlapping options (both $1$\ h and $2$\ h in two categories).
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**Ex.\ \@ref(exr:KidsEnvironmentQuestions).**
The first two are *closed*, with one option to be selected. The other is *open*.
I'm not sure primary school children could recall the answers to the first two questions accurately...
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### Chap.\ \@ref(DescribingVars): Classifying data {.unlisted .unnumbered}
:::::: {.ChapAnswers data-latex=""}
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**Ex.\ \@ref(exr:DescribeClassifying1).**
Quant.\ continuous.
Qual.\ nominal.
Quant.\ continuous.
Qual.\ nominal.
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**Ex.\ \@ref(exr:DescribeClassifying1B).**
Quant. discrete.
Qual. nominal.
Qual.\ nominal.
Qual. nominal.
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**Ex.\ \@ref(exr:DescribeClassifying2).**
False; true; false
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**Ex.\ \@ref(exr:DescribeClassifying2B).**
False; false; true.
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