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Stat Tutor

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0:37

Correct. The cloud of data in the scatterplot on the left is skinnier than the cloud of data in the plot on the right. Note that the labeling on the x- and y-axes are the same for both scatterplots.

Incorrect. The cloud of data in the scatterplot on the left is skinnier than the cloud of data in the plot on the right. Note that the labeling on the x- and y-axes are the same for both scatterplots.

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1:00

Correct. If you note the labeling on the x- and y-axes, you will see that the same data is plotted in both scatterplots.

Incorrect. If you note the labeling on the x- and y-axes, you will see that the same data is plotted in both scatterplots.

2

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1:33

Correct. This is a hard question as the cloud of data in the plot on the right is much skinnier than the cloud of data in the plot on the left. However, both clouds are parallel to the x-axis. The line drawn through both clouds would have zero slope—indicating no relationship between X and Y.

Incorrect. This is a hard question as the cloud of data in the plot on the right is much skinnier than the cloud of data in the plot on the left. However, both clouds are parallel to the x-axis. The line drawn through both clouds would have zero slope—indicating no relationship between X and Y.

2

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2:37

Correct. Computing correlation, r, requires both X and Y to be quantitative.

Incorrect. Computing correlation, r, requires both X and Y to be quantitative.

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3:01

Correct. Correlation should only be computed for X and Y when their relationship is linear.

Incorrect. Correlation should only be computed for X and Y when their relationship is linear.

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3:48

Correct. This is a correct statement.

Incorrect. This is a correct statement.

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5:27

Correct. While not strong, the direction of a line drawn through the cloud of data would have negative slope.

Incorrect. While not strong, the direction of a line drawn through the cloud of data would have negative slope.

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6:40

Correct. z-scores can be negative or positive. A positive z-score multiplied by a negative z-score gives a negative product.

Incorrect. z-scores can be negative or positive. A positive z-score multiplied by a negative z-score gives a negative product.

2

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7:23

Correct. This is a correct statement.

Incorrect. This is a correct statement.

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7:47

Correct. On a scale from zero to one, 0.54 is near the middle so it tells us that the strength is “moderate.”

Incorrect. On a scale from zero to one, 0.54 is near the middle so it tells us that the strength is “moderate.”

2

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9:10

Correct. This is a correct statement. All rectangles have red or pink colors.

Incorrect. This is a correct statement. All rectangles have red or pink colors.

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9:47

Correct. Since most of the rectangles have pink or red colors rather than blue colors, most of the products are positive.

Incorrect. Since most of the rectangles have pink or red colors rather than blue colors, most of the products are positive.

2

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9:59

Correct. The number of rectangles with pink and red colors is about the same as the number of rectangles with blue colors.

Incorrect. The number of rectangles with pink and red colors is about the same as the number of rectangles with blue colors.

2

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10:08

Correct. The number of rectangles with red and pink colors is less than the number of rectangles with blue colors.

Incorrect. The number of rectangles with red and pink colors is less than the number of rectangles with blue colors.

2

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10:27

Correct. All rectangles have blue colors.

Incorrect. All rectangles have blue colors.

2

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11:26

Correct. This is a correct statement.

Incorrect. This is a correct statement.

2

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12:00

Correct. Since the sign on “r” is positive, direction is positive.

Incorrect. Since the sign on “r” is positive, direction is positive.

2

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Correct. Since “r” is very close to “+1.0,” the strength is really strong.

Incorrect. Since “r” is very close to “+1.0,” the strength is really strong.

2

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12:35

Correct. Since the sign on “r” is negative, direction is negative.

Incorrect. Since the sign on “r” is negative, direction is negative.

2

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Correct. On a scale from zero to one, 0.553 is about halfway in between, so strength is moderate.

Incorrect. On a scale from zero to one, 0.553 is about halfway in between, so strength is moderate.

2

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13:49

Correct. Since the sign on “r” is negative, direction is negative.

Incorrect. Since the sign on “r” is negative, direction is negative.

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14:05

Correct. On a scale from zero to one, 0.226 is close to zero, so strength is weak.

Incorrect. On a scale from zero to one, 0.226 is close to zero, so strength is weak.

2

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Correct. First of all, a line drawn through the data will have positive slope, so “r” must also be positive. Second, there is too much scatter for “r” to be as high as 0.98. Of the answers given, 0.63 is the most reasonable.

Incorrect. First of all, a line drawn through the data will have positive slope, so “r” must also be positive. Second, there is too much scatter for “r” to be as high as 0.98. Of the answers given, 0.63 is the most reasonable.

2

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