Exam MAS-I Practice Question 138

Study guide: Exam MAS-I

Five scatter plots each show a response against a continuous predictor $x$ before any model is fitted. Match each description to what it most directly indicates for the model. An option may be used more than once or not at all.

Part a (1 point)

The points are centred along a rising straight line, tightly packed at low $x$ and spreading into a wide band at high $x$ , like a wedge.

A) Needs a transformation or non-linear term
B) Variance grows with the mean
C) High-leverage point to investigate
D) Little or no association
E) A categorical variable is missing

Part b (1 point)

The points form a narrow band that rises steeply at low $x$ and flattens out at high $x$ .

A) Needs a transformation or non-linear term
B) Variance grows with the mean
C) High-leverage point to investigate
D) Little or no association
E) A categorical variable is missing

Part c (1 point)

Two parallel bands of points each rise with $x$ , one sitting well above the other, with few points between them.

A) Needs a transformation or non-linear term
B) Variance grows with the mean
C) High-leverage point to investigate
D) Little or no association
E) A categorical variable is missing

Part d (1 point)

The points form a round, shapeless cloud, with no trend in either the centre or the spread across $x$ .

A) Needs a transformation or non-linear term
B) Variance grows with the mean
C) High-leverage point to investigate
D) Little or no association
E) A categorical variable is missing

Part e (1 point)

The points follow a straight rising line closely, except one point whose $x$ is far beyond all the others; it sits well below where the line through the rest would reach.

A) Needs a transformation or non-linear term
B) Variance grows with the mean
C) High-leverage point to investigate
D) Little or no association
E) A categorical variable is missing

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