iii.iv. from choices (a) through (e), identify the correlation of the following graphs. a).44 b).98...
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From choices (a) through (e), identify the correlation of the following graphs.
a) .44 b) .98 c) .92 d) -.89 e) -.99
For each pair of mean and median, determine which description best describes a distribution having those measures of center:
1. slightly skewed left2. slightly skewed right3. strongly skewed right4. strongly skewed left5. 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 70 45 46
•Find the 5-Number Summary of these scores.
•Make a stemplot of the scores.
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 64 66 65 70 65Men 72 68 70 68 74 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.