Sunday, June 23, 2013

Nice atheists and mean atheists? Malcolm X and Martin Luther King?

I've been at the Secular Students Alliance conference in Las Vegas for the last three days.  Lots of great stuff going on here.  My talk was yesterday.  Here's a link to my slide show:

Being an Out of the Closet Atheist

And the SSA will have a video of the talk up shortly.  I'll post a link when that becomes available.

Richard Carrier gave a good talk, and he's doing lots of good work.  He has a new book that looks good:

And he's got a video of an excellent primer on Bayes Probability Reasoning that is very clear, and has minimal math.

Tuesday, June 4, 2013

Confirmation Bias, Student Grades, and Prayer

This is the season, after grades have been submitted, when student emails complaining about grades come in. A particular pattern emerges. I couldn't resist writing it up to use in my Critical Thinking classes. The other obvious application of the Confirmation Bias point is to the way people often think about prayer.

Confirmation Bias is the mistake of selecting evidence that corroborates a pet hypothesis while ignoring or neglecting evidence that would disprove it. Humans are guilty of committing it in a wide range of circumstances. At the end of each semester, many students, including students in Critical Thinking and Theory of Knowledge where we study confirmation bias extensively, blunder into it. They get a grade for the course that is surprisingly low and send an email to their professor asking to know what happened. As far as they knew, they were doing great in the course. They recall getting an A on an assignment, and going ok on the midterm, and feeling pretty optimistic, so they can’t understand the low grade. Notice the parts highlighted in red here (a real email):

 Student 1: I just checked my grades for the Spring semester and was surprised to have earned an F grade. I completed the major assignments for the course and did well on the midterm (90%) and well on the final (85%). I know I didn't participate in the online forum as much as was required but I'm still confused about the grade. I took the class material seriously and did my best on every assignment assigned.

Professor McCormick (notice the grades highlighted in red here): Here are the grades I have for you. This syllabus gives the details about the grade structure. Check the math and check your returned assignments to make sure it's all right. If there's a clerical error, I'll fix it right away:
Question Sets: 0, 82, 0, 75, 0, 95 (6% each)
First paper: 78
Midterm: 90.5
Second paper: 85
Final: 85
Outside projects: 7/8
Google Group: 0/8 
Attendance and participation: 0/8 

So between the skipped question sets, the Group discussion and attendance, you gave up 34% of the grade. Even if you were making an A on everything else, that would put it down to a D.

 Student 2: I'm emailing you in regards to my final grades. I was hoping you could provide a detailed summary of my grades for the semester so that I can understand how I received a D. I felt as though I did fairly well, particularly improving on the more major assignments, so I would just like to know how I still failed to pass. If you could email me a detailed summary of my grades, I would greatly appreciate it. Thank you.

 Professor McCormick: Yeah, I was disappointed in your grades too. It seemed to me that you are capable of doing much better work, and being more responsible about turning stuff in. Here are the grades I have. Check the math with the grade structure on the syllabus and let me know if there is a clerical error asap: 

Question sets: 76, 0, 82, 0, 85, 56, 80 (6% each)
Evil paper 65
Midterm 68.5 
Second paper: 75
Final exam: 85
Outside Projects: 6/8
Google Groups: 4/8 
Attendance and participation: 6/8

So the skipped question sets took 12% off of your grade. You got a D on the first paper and didn't take the opportunity to rewrite it that I gave the class. You could have brought that up substantially. The Google Group points would have helped too since your overall score came out at 68%.

When we commit confirmation bias, we cherry pick the evidence that suits us. The student actively remembers the good grades, but missed assignments and low scores are forgotten. But clearly, having an accurate and objective grasp of the relevant evidence would serve us well. We don’t want to ignore evidence indicating something negative, disastrous, or dangerous because it doesn’t suit what we want to be true. Imagine if a doctor acquired a skewed view of the evidence concerning a potentially fatal disease this way. Suppose the Secretary of State ignored significant negative indicators in the behavior of an aggressive and hostile foreign country. Suppose a potential employer asked you how you did in your Critical Thinking course in college, and then she checked your transcripts against your distorted report. Suppose you spend thousands of dollars over the years on losing lottery tickets because the occasional wins stick out in your mind so prominently, while the loses are forgotten.  Suppose you spend time praying to God frequently, hundreds or thousands of times in your life, and on the rare occasion when something vaguely resembling what you prayed for came true, you count that as an answered prayer, while ignoring the thousands of misses.  Suppose you sustain your belief in God for years on the basis of this mistake.