March 19, 2014

Moving towards standards-based grading

I've been taking baby steps towards standards-based grading (SBG) for over two years, but this semester is the first time that I've really implemented the core ideas of SBG in any of my classes.

Last Fall I had (with my colleague) the opportunity to rewrite learning outcomes for our introductory astronomy course, ASTR101.  This is a general education survey of astronomy course without a laboratory. It is 3 credit hours and covers the solar system, stars, and galaxies.

Our campus assessment specialist pushed us to look at the revised Bloom's taxonomy word list to come up with descriptors for what we wanted our outcomes to be.  I really don't like how our campus uses the Bloom's taxonomy, but my opinions are a topic for another time.

After the outcomes were written and approved, I realized that I could implement them almost unchanged as standards for a real step towards SBG.

Here's what I did:

I went from 3 exams plus a final to no midterm exams, but nearly weekly quizzes. Each quiz is "scored" on a 0-5 point scale which measures the mastery of the standard being assessed. Students have optional homework assignments on MasteringAstronomy (which, by the way, is NOT optimized for SBG) but they are required to do the homework if they want to re-assess by retaking the quiz. If they want to retake the quiz for a third time, they have to visit my office for a discussion about the standard before they are allowed a third shot.  After the third try, the standard is closed.

Grades are weighted - 40% is based on a semester-long astrojournal, 35% is the SBG-style quizzes, 10% is a Just-in-Time-Teaching style reflection/reading review that students submit online, and 15% is a cumulative final.

So far, I've had a fairly positive experience with this in astronomy.  I should write down my workflow for getting all the assessments prepared and scored.  I have had some students come in for reassessments.  I am expecting to see more as the semester progresses.

What I could really use is a bit of feedback on how the standards are written.  I can't change the learning outcomes, but I can tweak the standards if appropriate.

There are some standards broken into multiple parts so I could have the option if necessary to break out into multiple assessments.  The goal was to have no more than 15-16 assessments. Here's the standards as I wrote them out:

1) Explain how astronomical objects move in the sky.

2a) Explain the cause of the seasons

2b) Explain the cause of moon phases.

2c) Explain the cause of eclipses.

3) Describe how the heliocentric model of the solar system was developed and why it was adopted over the geocentric model of the universe.

4a&b) Apply Kepler's Laws of orbital motion and Newton's Law of Universal Gravitation to objects in the universe.

5) Describe the functions of a telescope and types of telescopes and explain why some telescopes are placed on the ground and some in space.

6) Explain how astronomers use light to determine:
           a.) the luminosity of stars,
b.) temperature of stars,
c.) and size of stars,
d.) chemical composition of astronomical objects,
e.) the speed and direction of an astronomical object's motion,

7) Describe the nature of our solar system and how it was formed.

8) Explain how astronomers use the Hertzsprung-Russell diagram to study properties of stars.

9) Describe how stars are formed, evolve and die.

10) Describe the structure and size of the Milky Way galaxy.

11) Compare the Milky Way galaxy to other galaxies.

12) Explain how astronomers know that the universe is expanding and how they determine the age of the universe.

March 18, 2014

Distances to brightest naked eye stars

I saw this recent xkcd comic, and had to figure out how many of the naked eye stars are more than 1000 light-years away.

It took me awhile to find a star catalog that was easy to search which also had both the apparent magnitudes and the distances to the stars, but I was able to locate a database of over 87,000 stars in CSV format.

First I found all the stars with magnitude 6.0 or brighter. That narrowed the list down to just over 5,000 stars. Putting the distances into, I created this histogram:

Each bar represents a bin of width 100 parsecs. My interest in stars 1000 light-years means I have to look at the stars more than 300 parsecs away. I added up the stars in the first three bins, which represented about 87% of all the visible stars.  So my estimate of the naked eye stars which are 1000 light-years away or more is about 13%.

So, assuming on a clear night (no moon, ideal viewing conditions) I could see somewhere between 2000-3000 stars total, only about 250-400 stars would be more than 1000 light years away.

Of course, looking through a telescope changes that figure completely.

March 16, 2014

Suggesting twitter to high school teachers did not go well

Recently I had the opportunity to have dinner with high school science teachers from our college's district.  Our department hosted what we call a Science Dinner, which was an open house and a meal after the teachers had a chance to visit labs in the department.

During dinner, the conversation drifted from one topic to the next, including how schools were implementing Next Generation Science Standards, how to implement AP Physics, and the lack of funds for professional development.

I asked the teachers (including a department head) if they had ever thought of exploring online options for professional development such as twitter or facebook. I explained that there are teachers from all over the country on twitter who are asking similar questions and discussing issues which traditional professional development funds would typically cover.  I offered to put all the physics teachers in touch with physics teachers on twitter all over the country if they were interested.

The teachers all listened politely and said that they had never considered online professional development. One of them said that another teacher at her school had quit last year over an interaction that happened on social media. Another teacher said that she would never want to be on twitter because her students might be on twitter, and she would not want to interact with them online.

I was stunned at how quickly the conversation turned to pointing out the dark sides of social media. I had this naive idea that interacting with other teachers from around the country would be really attractive. I guess I underestimated the fear of the unknown.

Next time I have the opportunity to plug social media, I'm going to suggest starting with The Global Physics Department first.  Perhaps that is an avenue to getting teachers to interact with each other online.