15.071 | Spring 2017 | Graduate

# The Analytics Edge

4.2 Judge, Jury, and Classifier: An Introduction to Trees

## 4.2 Judge, Jury, and Classifier: An Introduction to Trees

### Quick Question

Suppose you have a subset of 20 observations, where 14 have outcome A and 6 have outcome B. What proportion of observations have outcome A?

Exercise 1

Numerical Response

Explanation

The fraction of observations that have outcome A is 14/20 = 0.7.

### Quick Question

The following questions ask about the subset of 20 observations from the previous question.

If we set the threshold to 0.25 when computing predictions of outcome A, will we predict A or B for these observations?

Exercise 2

A

B

If we set the threshold to 0.5 when computing predictions of outcome A, will we predict A or B for these observations?

Exercise 3

A

B

If we set the threshold to 0.75 when computing predictions of outcome A, will we predict A or B for these observations?

Exercise 4

A

B

Explanation

Since 70% of these observations have outcome A, we will predict A if the threshold is below 0.7, and we will predict B if the threshold is above 0.7.

## Course Info

Spring 2017
##### Learning Resource Types
Lecture Videos
Lecture Notes
Problem Sets with Solutions