R 作业代写代编代码Thinking and Reasoning

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R 作业代写代编代码Thinking and Reasoning
MAST90044 Thinking and Reasoning with Data
Instructions
? Assignments are to be placed in the appropriate subject and lab box located just inside the north
entrance to the Peter Hall Building. Assignments must be stapled.
? Please label your assignment with the following information:
– your name;
– your student number;
– your lab class;
– your tutor’s name.
? You must sign the plagiarism declaration. The link is available on the LMS.
? Your assignment should show all working and reasoning, as marks will be given for method as well as
for correct answers. Please spell check your document.
? Paste any R code and output into the appropriate places so that it can be seen easily along with your
other work. Graphics from R can be resized within your document; make them smaller as necessary.
? Assignments count for 50% of the assessment in this subject. This one is worth 15%, and covers the
work done in chapters 4 to 6.
? Tutors will not help you directly with assignment questions. However, they may give some help with
R.
? Solutions to the assignment questions will be made available later.
MAST90044 Thinking and Reasoning with Data Assignment 1
Contemporary Issues in Crime and Justice Number 115
May 2008
This bulletin has been independently peer reviewed.
Does circle sentencing reduce Aboriginal
offending?
Jacqueline Fitzgerald
Circle sentencing is an alternative method of sentencing Aboriginal offenders which involves the
offender’s community in the sentencing process. This bulletin considers whether people who
participate in circle sentencing (1) show a reduction in the frequency of their offending, (2) take
longer to reoffend and/or (3) reduce the seriousness of their offending. The results suggest that
circle sentencing has no effect on any of these outcomes. Circle sentencing participants offended
less in the 15 months following their circle. However, the same was also true of Aboriginal people
sentenced in a traditional court setting (the control group). After a range of offender and offence
characteristics were controlled for, we found no difference between the circle sentencing group and
the control group in time to reoffend. Finally, there was no difference between the circle sentencing
group and the control group in the percentage of offenders whose next offence was less serious
than the reference offence.
Introduction
Circle sentencing is an alternative
sentencing process for adult Aboriginal
offenders in New South Wales. It takes
the sentencing process out of the
traditional court setting and allows the
involvement of the offender’s community.
In a circle sentence, the offender,
magistrate, community elders and (on
occasion) the victim and support people
for the offender and/or victim sit in a circle
to discuss the circumstances and impact
of the offence and determine a sentence
tailored to the offender. Circle sentencing
has the full sentencing powers of the
court (Crime Prevention Division 2007).
The first circle sentence in New South
Wales was conducted in Nowra in
February 2002. Since then, with the
exception of an early review of the first
12 months of operation, a rigorous
evaluation of circle sentencing has not
been published. In 2006, the New South
Wales Attorney General’s Department
commissioned a comprehensive
review of the impact of all aspects of
circle sentencing. As part of this review,
the Bureau of Crime Statistics and
Research was asked to analyse the rate
of reoffending among circle sentencing
participants. This bulletin reports the
results of these analyses.
Background
The circle sentencing process that
operates in New South Wales was
adapted from a program that originated
in Canada in the early 1990s for the
sentencing of Indigenous offenders (Potas
et al. 2003). The Canadian program is
based on a restorative model of justice,
which seeks to reconcile the offender and
the victim and actively engage community
members in the rehabilitation of the
accused (LaPrairie 1995).
All Australian jurisdictions, with the
exception of Tasmania, now operate an
Indigenous sentencing court of some
type. The procedures in these courts
generally follow the tenets of restorative
justice, such as, improving communication
between parties, applying procedural
justice (that is, treating people respectfully
and fairly), using persuasion and support
to encourage offenders to be law-abiding
and to avoid incarceration (Marchetti
& Daly 2007). In addition, Indigenous
sentencing courts endeavour to be
culturally appropriate, being inclusive of
both the Indigenous community and the
offender (Marchetti & Daly 2007).
At the time of writing in New South
Wales circle sentencing was operating
in Armidale, Bourke, Brewarrina, Dubbo,
Kempsey, Lismore, Mt Druitt and Nowra.
Nearly half of all circle sentences involve
an offence of common assault; the next
most prevalent offences are unlicensed
driving and breaching an apprehended
violence order.
The eight objectives of circle sentencing
in New South Wales are set out in
Schedule 4 of the NSW Criminal
Procedure Regulation 2005. They are:
To include members of Aboriginal
communities in the sentencing process
To increase the confidence of
Aboriginal communities in the
sentencing process
a)
b)
CRIME AND JUSTICE
Bulletin NSW Bureau of Crime
Statistics and Research
Q1 We will consider issue (3) in the abstract above – whether people who participate in circle sentencing
reduce the seriousness of their subsequent offending. The following table from the article, which considers
subsequent offenders, gives the frequencies and percentages upon which the authors’ conclusion
was based.
B U R E A U O F C R I M E S T A T I S T I C S A N D R E S E A R C H
offence, prior convictions and prior
incarceration, there was no significant
difference between circle sentencing
participants and the control group in
time to reoffend. The answer to the third
question is that there was no significant
difference between the treatment and
the control group in the percentage of
offenders whose next offence was less
serious than the reference offence.
Taken as a whole, the evidence presented
here suggests that circle sentencing
has no effect on the frequency, timing
or seriousness of offending. It could
be argued that these results may have
been different with a more extensive
set of controls. However, this is unlikely
for at least two reasons: the findings
are consistent and an extensive set of
controls were employed in analysing time
to reoffend. The only positive effect for
circle sentencing that even approached
significance was the change in offence
seriousness for circle sentencing
participants, relative to Aboriginal
people dealt with in a conventional court
proceeding (p=0.056 in the one-tailed
Fisher Exact test). Even this effect,
however, might be just a reflection of
regression to the mean.
It should not be concluded that circle
sentencing has no value simply because
it does not appear to have any shortterm
impact on reoffending. Reducing
recidivism is just one of several objectives
of the process. There is nothing in this
analysis to suggest that circle sentencing
is not meeting the other objectives. If it
strengthens the informal social controls
that exist in Aboriginal communities,
circle sentencing may have a crime
prevention value that cannot be quantified
through immediate changes in the risk of
reoffending for individuals.
Given the high priority attached by the
Government to reducing reoffending (see
NSW Government 2006), however, it
would seem prudent to begin considering
ways in which the effectiveness of circle
sentencing in reducing reoffending might
be improved. MacKenzie (2002, p. 385)
argues that, to be effective, rehabilitation
programs must change the characteristics
of offenders that are associated with
their criminal activity (e.g. association
with criminal peers, poor impulse control,
alcohol and drug abuse, unemployment).
The circle sentencing process is not
designed to do this. Instead, it seeks
to, amongst other things, reduce
reoffending by giving Aboriginal people
direct involvement in the sentencing of
Aboriginal offenders. The results reported
here suggest that such direct involvement
is not enough, by itself, to produce a
reduction in reoffending. Consideration
should perhaps be given to combining
circle sentencing with other programs
(e.g. cognitive behavioural therapy, drug
and alcohol treatment, remedial education)
that have been shown to alter the risk
factors for further offending (MacKenzie
2002; Aos, Miller & Drake 2006).
Notes
Another problem is that, from the
Productivity Commission’s published table,
it is unclear how Harris derived an overall
reoffending rate of 29.4% which he cites for
the comparison group.
Offences which were brought to court but
for which the person was not convicted
were not counted. It should be noted
that offences proven in court are not a
precise measure of recidivism as they
exclude crimes for which the offender is
1.
2.
not apprehended. Alternative indicators,
such as police mentions or self-reported
offending, however, have as many, if not
more, problems. Offenders asked to report
on their own offending may not answer
truthfully. Police contacts that do not result
in a conviction may reflect biases in the
exercise of police discretion.
Information on proven offences was
obtained from the Reoffending Database
of the Bureau of Crime Statistics and
Research. See Hua & Fitzgerald 2006 for
details.
A 15-month follow-up period was chosen to
balance the benefits of a reasonable followup
period with the need for a reasonable
sample size. A longer follow-up period
would give a better indication of a person’s
offending patterns. However, it would also
restrict the analysis to a small number of
people circle sentenced in the early days
of the program. For instance, a 30-month
follow-up period would include only 49
individuals who participated in a circle
sentence between 2002 and 2004. Eightyone
individuals participated in a circle
sentence prior to January 2006.
At the time the analysis was conducted
information was only available on court
appearances finalised up to 30 June 2007.
As a result, individuals in both the circle
sentencing group and the control group may
have committed offences in the 15 month
follow-up period which had not yet been
finalised in court by 30 June 2007. The effect
of this on the circle sentencing group and the
control group should be the same.
Offences committed before the circle
sentence (or equivalent reference court
appearance) but finalised in court after it
were counted as prior convictions.
Twenty five percent of both the circle
sentencing group and the control group had
spent time in prison in the five years prior to
the reference court appearance.
An alternative to omitting the seven
individuals for whom an accurate control
group member could not be found, would
have been to relax the matching criteria. It
was decided that it was preferable to have
a slightly smaller sample size with a control
group that precisely represented the circle
sentencing group rather than additional
subjects with a less representative control
group.
Only offences proven in court up to June
2007 were included.
3.
4.
5.
6.
7.
8.
9.
Table 5. Change in offence seriousness by method of disposition
– Circle sentencing group versus Control group
Seriousness of
subsequent offence
Circle sentencing group Control group
No. % No. %
Less serious 34 55.7 3690 44.7
More serious or the same 27 44.3 4560 55.3
Total 61 100 8250
n.s.a
100
a. Not significant: c2
= 2.968, d.f. = 1, p=0.085, Fisher’s Exact Test p=0.056
(a) Enter the data into R and perform a suitable test to examine the association between seriousness
of subsequent offence and sentencing group (Circle vs Control). Interpret the result of the test in
terms of the 0.05 significance level. Give some justification for the test that you have used.
(b) From first principles, calculate the expected frequency for the top left hand cell of the table (Less
serious × Circle sentencing group) under the null hypothesis of no association.
(c) 55.7% of the Circle sentencing group had less serious subsequent offences, but only 44.7% of the
Control group did. The authors concluded that “there was no difference” between the groups (last
sentence of abstract). Were they justified in this conclusion? Briefly explain.
(d) Test whether a claim that “half of those who participate in circle sentencing commit less serious
subsequent offences” is reasonable.
2
MAST90044 Thinking and Reasoning with Data Assignment 1
Q2 An investigator wished to determine whether epinephrine has the effect of elevating plasma cholesterol
levels in humans. Twelve adult males were selected and given both a placebo and the drug. Blood
samples were taken following injection of the placebo and again after injection of epinephrine. Analysis
of the blood samples resulted in the following data:
| Cholesterol Levels (mg/100ml)
Subject | Placebo Epinephrine
--------|--------------------------------
1 | 178 184
2 | 240 243
3 | 210 210
4 | 184 189
5 | 190 200
6 | 181 191
7 | 156 150
8 | 220 226
9 | 210 220
10 | 165 163
11 | 188 192
12 | 214 216
(a) Formulate an appropriate statistical model, defining all the terms. State the null and two-sided
alternative hypotheses which reflect the research question of interest.
(b) Enter the data into R, and calculate the means for placebo and epinephrine. Find a 95% confidence
interval for the mean difference in cholesterol levels between the placebo and epinephrine. Use the
confidence interval to test your null hypothesis.
(c) Would a 99% confidence interval contain zero? Briefly explain. (You don’t need to actually
calculate the 99% confidence interval to answer this question.)
(d) Perform a test which addresses the research question but makes no assumption about the two
populations being normally distributed. Compare the P-value for this test with the P-value found
in (b). Comment on why one is substantially larger than the other.
Q3 A study of customer service compared the waiting time on telephone transactions of two different types.
A random sample of 12 calls to a community information service was taken. A separate random sample
of 12 calls to book AFL final tickets was taken. For each call, the time in minutes spent ‘on hold’ was
recorded. The data are given below.
Community service 11.2 14.1 9.0 6.9 12.6 15.4 18.3 14.3 10.6 9.4 12.1 11.3
AFL final tickets 6.1 4.7 8.3 9.0 10.5 9.2 12.5 6.4 11.6 9.7 12.2 8.6
(a) Enter the data into R. Produce an appropriate graphical display of the data, and calculate the
sample mean and standard deviation for both groups. What conclusions can you draw from these
results?
(b) Find a 95% confidence interval for the difference between the mean waiting times for the two types
of transactions. Is it reasonable to claim that AFL final tickets require a shorter waiting time?
(c) The customer service manager claims that the average waiting time for community service calls is
10 minutes. Is this claim consistent with the data?
3
MAST90044 Thinking and Reasoning with Data Assignment 1
Q4 It is possible to count bunches of grapes long before they are harvested. It would be convenient for
the grower if the weight of the bunches harvested could be reasonably predicted from the number of
the bunches. For this question, we will ignore the treatment and the other explanatory variables in the
data.
For this question you will find the data in the file winery.xls. You will need to figure out how to import
the relevant data into R to answer these questions.
(a) Represent the relationship graphically between the number of bunches harvested and the weight
harvested, for 2001.
(b) Would you describe the relationship as strong? Give a reason, based on a suitable summary
statistic.
(c) Describe an appropriate statistical model for examining the research question, and fit the model in
R. Examine appropriate diagnostic plots, and comment on anything that challenges the assumptions
of the model.
(d) Find a 95% prediction interval for the weight when the number of bunches is 30. Explain its
meaning.
(e) Suppose someone looks at the analysis that you have carried out and comments:
“I don’t understand. If I plug in zero bunches in your estimated model, I don’t get a
prediction of zero weight. How come? That can’t be right!”
Respond to this objection.
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