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Lecture 19
This lecture will cover some questions similar to
those you may find on Exam 2.
These are among the “nonstandard” questions;
they are not exactly like the homework exercises.
In addition, there will be many “standard”
questions similar to the homework exercises.
200
150
0
50
100
Frequency
250
300
350
1. A sample of n = 1000 observations is summarized by
the histogram below. Which
ofofthe
following statements
Histogram
x
is false?
0
50
100
150
200
x
A. The distribution is right-skewed.
B. The median is below 50.
C. This population is not normally distributed.
D. The range could be about 200.
E. More than 50% of the observations lie above the median.
2. What are the mean and standard deviation of the
normal distribution shown below?
95%
80
A. µ = 80,
σ = 120
B. µ = 10,
σ = 100
C. µ = 20, σ = 100
D. µ = 100, σ = 10
E. µ = 100, σ = 20
100
120
3. With respect to this boxplot, which of the following
statements is false?
0
20 40 60 80 100 120
A. The distribution is symmetric.
B. The median is 60.
C. The interquartile range is 40.
D. The range is 100.
E. 75% of the sample lies above 50.
4. Suppose a population is normally distributed
with mean 10 and standard deviation 1.
Which of the following measurements should be
considered an outlier?
A. 11
B. 12
C. 9.5
D. 6
E. 8.2
5. Suppose a linear regression analysis produces the
following result:
Y = 15 + 5 X
Which of the following statements is definitely true?
A. The intercept is not a reliable prediction for Y when X=0.
B. The variables X and Y are positively correlated.
C. When X=2, the predicted value of Y is 20.
D. The variables X and Y are causally related.
E. If X increases by 1, the average value of Y
increases by 15.
6. Which of the following statements is false?
A. The median is the same thing as the 50th percentile.
B. 75% of a sample lies between the 25th percentile and
the maximum.
C. The mean is the same thing as the average.
D. The standard deviation can never be negative.
E. The mode can never be equal to the minimum.
7. Scores on a test are normally distributed with mean
40 and standard deviation 8. A student who scores
52 is at what percentile?
A. 78th percentile
B. 85th percentile
C. 90th percentile
D. 93rd percentile
E. 95th percentile
1000
0
500
births
1500
2000
8. This scatterplot shows X = number of UFO sightings and
Y = number of live births in thousands (2000-2004) for
the fifty states. Which of the following statements is false?
0
10
20
30
40
ufos
A. The average value of Y increases as X increases.
B. This is probably an example of Simpson’s paradox.
C. The is probably an example of a spurious correlation.
D. The relationship between X and Y is not causal.
E. States with more UFO sightings have more live births.
9. Refer to the stem plot at the right.
Which of these statements is false?
A. The range is 92 – 44 = 48.
B. There are two modes.
C. The median is 73.
D. The interquartile range is about 50.
E. There are no outliers.
4
5
4
1 4
6
7
8
2 2 9
3 5
0 1 5
9
2 2
300
200
sales
400
500
10. This plot below shows average daily sales (in thousands
of dollars) for a large supermarket from 1990 to 2005.
Which of the following statements is true?
1990
1995
2000
2005
year
A. Linear regression is appropriate.
B. X and Y are uncorrelated.
C. X and Y are causally related.
D. Average daily sales in 2005 were above $500,000.
E. The linear regression prediction for 2000 is too low.
0
10
20
30
y
40
50
60
70
11. What is the correct equation for this regression line?
A. Y = 6 + 10 X
B. Y = 10 – 6 X
C. Y = 10 + 60 X
D. Y = 10 + 5 X
E. Y = 10 – 5 X
-2
0
2
4
6
x
8
10
12
See you on Wednesday!