# STAB22H3 Midterm: STAB22H3 Midterm 2008 Winter QuestionExamPremium

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StatisticsCourse Code

STAB22H3Professor

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MidtermThis

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STAB22 Midterm Examination

March 2008

For this examination, you are allowed one handwritten letter-sized

sheet of notes (both sides) prepared by you, a non-programmable,

non-communicating calculator, and writing implements.

This question paper has 13 numbered pages; before you start,

check to see that you have all the pages. There is also a signature

sheet at the front and statistical tables at the back.

This examination is multiple choice. Each question has equal

weight. On the Scantron answer sheet, ensure that you enter your

last name, ﬁrst name (as much of it as ﬁts), and student number

(in “Identiﬁcation”).

Mark in each case the best answer out of the alternatives given

(which means the numerically closest answer if the answer is a

number and the answer you obtained is not given.)

Before you begin, check that the colour printed on your Scantron

sheet matches the colour of your question paper. If it does not,

get a new Scantron from an invigilator.

Also before you begin, complete the signature sheet, but sign it

only when the invigilator collects it. The signature sheet shows

that you were present at the exam.

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1. A linear regression was carried out for predicting one variable yfrom another variable x. The residuals

from the regression were calculated and plotted against x. The plot is shown below.

What do you conclude from this plot?

(a) There is no evidence for a straight-line relationship at all between yand xfrom this graph.

(b) A straight-line relationship between yand xis a satisfactory ﬁt.

(c) The relationship between yand xis obviously curved.

(d) In the relationship between yand x,yis predicted more accurately for smaller values of xthan

for larger values.

(e) To assess the strength and form of the relationship between yand x, it is enough to look at the

correlation; there is no need to look at the residual plot.

2. Use the information below for this question and the following two questions.

Scores on a standardized test for children have mean 50 and standard deviation 10, and they follow a

normal distribution.

What proportion of children will score above 65 on this test? (Mark the closest answer below if your

answer does not appear.)

(a) 0.50

(b) 0.93

(c) 0.20

(d) 0.80

(e) 0.07

3. Using the information in Question 2, what proportion of children will score between 45 and 65? (Mark

the closest answer below if your answer does not appear.)

(a) 0.94

(b) 0.31

(c) 0.50

(d) 0.08

(e) 0.63

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4. Using the information in Question 2, the lowest 5% of children will score less than what value?

(a) 58

(b) 41

(c) 67

(d) 50

(e) 33

5. Some people seem not to gain weight even when they overeat. This might be explained by ﬁdgeting

and other “non-exercise activity” (NEA). In an experiment, researchers deliberately overfed healthy

young adults for 8 weeks. They measured fat gain (in kilograms) and the increase in energy use (in

calories) form activities other than deliberate exercise (NEA).

The NEA increase values had mean 324.8 and SD 257.66 calories; the fat gains had mean 2.388 kg and

SD 1.1389 kg. The correlation between fat gain and NEA increase was −0.7786. What is the intercept

of the least-squares regression line for predicting fat gain from NEA increase?

(a) −1.2

(b) 1.2

(c) −0.003

(d) cannot be calculated because necessary information is missing

(e) 3.5

6. For this question and the next, what graphical display would be most appropriate for the variable

described?

The number of hours per week students study during a semester?

(a) Pie chart

(b) Scatterplot

(c) Bar chart

(d) Histogram

(e) Both pie charts and bar charts are equally good for displacing the distribution of the variable

involved here.

7. Which radio stations are the students favorites?

(a) Stemplot

(b) Bar chart

(c) Boxplot

(d) Scatterplot

(e) Histogram

8. Scores on an exam are normally distributed with a mean of 68 and a standard deviation of 9. Using

the 68-95-99.7 rule, what percentage of students score above 77?

(a) 5%

(b) 32%

(c) 2.5%

(d) 16%

(e) 68%

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