The Bias Study

Happy New Year from Galaxy Zoo! 2007 has already left for some of you, and for others, it will be leaving soon. 2007 has been a great year for the study of galaxies, thanks to the galactic classifications that you have completed. I thought that in today’s post, I’d tell you a little more about what we are doing right now, as 2007 turns to 2008. Chris originally posted about this in the forum, and Kate has been providing a status update.

In last Thursday’s blog post, Chris gave an introduction to projects that the team is now working on. When he talked about Kate and Anze’s cosmology study (finding the rotation directions of spirals), he mentioned that a key to this project was completing the bias study. That “bias study” includes the rotated, mirrored, and black-and-white galaxy images that we’re asking you to classify now.

For those of you that aren’t familiar with what scientists mean by “bias,” it’s one of those funny words that has a specific meaning in science that is different from its meaning in everyday life. When we say “bias” in daily life, we often mean that someone has an agenda that means they can’t be trusted. For example, we might say that a news organization has an [insert political viewpoint] bias that means you just don’t trust that they’re giving you an accurate picture of the news.

That’s not what we mean here, though! There are several related meanings of the word “bias” in science, but they all come down to the question of whether results were influenced by some factor that the scientists didn’t think about. The scientist might ask himself or herself: Did I really study everything I could have studied? Did I do the right type of analysis on the data? Did I have some preconceived idea that kept me from interpreting the data with an open mind?

The question that we are asking is about how people see galaxies. When you see a fuzzy galaxy, is it easier to see it as an anticlockwise spiral than a clockwise spiral?

We’ve talked with some colleagues from psychology, and there is no reason to think that should be the case – but we want to test the idea just the same. That’s why we’ve introduced the rotated and mirrored galaxy images. The mirror image of a clockwise spiral should appear anticlockwise, and vice versa. So, all the clockwise galaxies in our original data should now appear anticlockwise in the “bias study data,” and vice versa.

The specific type of bias we’re looking for is called sample bias. Scientists often take a sample of a thing by measuring properties of some number of that thing. We’ve asked you to classify many galaxies, and the sample consists of your classifications. If, as mentioned above, humans classify anticlockwise galaxies easier, then the classification sample will have more anticlockwise galaxies than the real universe. If our sample of galaxy classifications is not the same as the classifications of galaxies in the real universe, then any conclusions we draw about the universe from our sample will be wrong.

And we don’t want to be wrong. Scientists are, by nature, very careful. We want to think of every possible effect, and every possible interpretation of our data, before deciding on the right one. By being as careful as we can, we hope to increase our understanding of the real universe in which we live.

As always, we need your help to do this. See Kate’s status update on the forum, and keep classifying those galaxies!