Transcript Dr. Hunter had just given an exam to nine students

From choices (a) through (e), identify the correlation of the following graphs.
a) .44
b) .98
d) -.89
c) .92
2
2
1.5
1.5
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1
0.5
0.5
0
0
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0.6
0.8
1
1.2
-0.5
0
0
0.2
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0.8
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1.2
-0.5
-1
-1
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1.5
1.5
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1
0.5
0.5
0
0
0
-0.5
e) -.99
0.2
0.4
0.6
0.8
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1.2
0
-0.5
-1
-1
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0.4
0.6
0.8
1
1.2
For each pair of mean and median, determine which description best describes a
distribution having those measures of center:
1.
2.
3.
4.
5.
slightly skewed left
slightly skewed right
strongly skewed right
strongly skewed left
approximately symmetric
a. mean = 24.1, median = 29.1
b. mean = 29.7, median = 29.1
c. mean = 32.5, median = 31.2
d. mean = 29.6, median = 24.2
Dr. Hunter had just given an exam to nine students. These were their grades:
67
64
70
51
63
35
•Find the 5-Number Summary of these scores.
•Make a stemplot of the scores.
70
45
46
A student wonders if people of similar heights tend to date each other. She
measures herself, her dormitory roommate, and the women in the adjoining
rooms; then she measures the next man each woman dates. Here are the
data (heights in inches)
Women 66
Men
72
64
68
66
70
65
68
70
74
65
69
Sketch a scatterplot of these data. Describe the pattern you observe.
Which of the following statements is true?
1. The variables measured are all categorical.
2. There is a negative correlation between the heights of men and women, since
the women tend to be shorter than the men they date.
3. There is a positive correlation between the heights of men and women.
4. Correlation makes no sense here since gender is a categorical variable.
The correlation coefficient measures
A) whether there is a relation between two variables.
B) whether or not a scatterplot shows an interesting pattern.
C) whether a cause and effect relation exists between two variables.
D) the strength of a straight line relation between two variables.
Scores on a certain IQ tend to be Normally distributed
with mean 125 and standard deviation 4.5.
What percentage of scores are higher than 130?
How low are the lowest 25% of scores?
Association Is Not Causation
• Give an example of two variables
illustrating this principle.
• For your example, what third, lurking
variable might explain the association?
Influential Observations
• Sketch a scatterplot with an influential
observation that is an outlier in the y
variable.
• Sketch a scatterplot with an influential
observation that is an outlier in the x
variable.
• Sketch a scatterplot with an outlier in the y
variable that is not influential.