Quiz 2

Milestones

Rubric

All questions on the quizzes in this course are out of 3 points. When assessing these quizzes, score answers as follows:

• 3 is reserved for excellent responses that that fully explain the answer to the question, show a true understanding of the question being asked, and don’t contain any errors. As a general guideline, we expect no more than 25-30% of answers are likely to receive a 3 on any particular question.
• 2 is awarded for a good response that’s getting at the right idea, but might not explain it fully or might have a few minor errors. 2, indeed, is what the course expects most students are likely to earn. As a general guideline, we expect approximately 50-60% of answers are likely to receive a 2 on any particular question.
• 1 is awarded for an inadequate response that misses the mark, is wholly incorrect, or otherwise fails to answer what the question is asking.
• 0 is given to answers that are exceedingly brief, or blank, and as such are effectively non-responses.

The above rubric should be applied for all questions on the quiz.

If you give a score lower than full credit, please include a brief comment in the “Provide comments specific to this submission” section of the form. You can also re-use comments in the “Apply Previously Used Comments” to save time so that you don’t find yourself typing the same thing over and over!

Grading Responsibilities

Answer Key

Question 1

1. 1/4 = 0.25
2. 4/13 ≈ 0.308
3. 1/221 = 0.005
4. 1/17 ≈ 0.059

Question 2

1. P(2H) = 0.25
2. P(1H, 1T) = 0.5
3. P(2T) = 0.25

Question 3

1. Yes. The arrow from Train to Appointment means that the Appointment distribution is conditional on the Train distribution.
2. Yes. The arrow from Maintenance to Train means that the Train distribution is conditional on the Maintenance distribution.
3. Yes. The arrow from Maintenance to Train and then from Train to Appointment means that Appointment is conditional on Train, which is conditional on Maintenance.
4. No. Given that we know the value of Train, no other variables affect the Appointment distribution.

Question 4

1. 0.012
2. 0.028
3. ≈ 0.429