Attention Victoria - there is a better blooming way!

stat403flower

The Victoria Flower Count is an annual light-hearted promotion sponsored and organized by regional chambers of commerce, Butchart Gardens and Tourism Victoria to "count" the number of flower blossoms while the rest of Canada is often covered in snow. The promotion relies on self-reporting by the public on their website http://www.flowercount.com/. According to their facebook site, almost 5 billion flowers were "counted" in Victoria proper and almost 22 billion for Greater Victoria.

However, Statisticians know that such surveys often provide little useful information because there is no control on the quality or quantity of data. For example, the same person could enter a count multiple times on the web page. Or, the same flowering tree and patch of flowers could be counted multiple times by different people. The students of Stat-403, a course in statistical methods for environmentalists and resource managers offered at Simon Fraser University across the strait in Metro Vancouver, decided to combine statistical theory and technology to come up with a better way.

According to the rules of the flower count, large/medium/small trees are assigned a value of 750,000, 500,000, or 250,000 blossoms, while other flower patches are assigned much smaller values. The number of trees essentially drives the count and so it is necessary only to count the number of trees in bloom.

The students in the class under the direction of their teaching assistant first selected 78 segments of streets from Victoria proper at random based on a list of street segments provided by the city. Then students used Google Street View to look at these segments of streets over the web and count the number of cherry trees visible from the street. Because Google Street view is not in real time, it was implicitly assumed that all cherry trees seen would be in bloom. The average number of trees per street segment was then expanded to cover the segments not sampled to give an estimate of 5.6 billion (with a margin of error of 1.8 billions) blossoms compared to the value of almost 5 billion counted by the Victoria Flower Count. There is likely a small amount of under-coverage because not all trees are visible from Google Street view (e.g. in resident's backyards) or some trees have been replaced since Google Street view took their video, or students cannot always recognize cherry trees, but the errors are likely to be immaterial. This method could easily be extended to all the surrounding municipalities.

This type of interdisciplinary work is a hallmark of our program in Applied Statistics at Simon Fraser University. For more information, please contact the course instructor Carl Schwarz (cschwarz@stat.sfu.ca), or the course teaching assistant Ryan Lekivetz (ralekive@sfu.ca). Members of the Stat-403 class who participated in the "flower count" are: Juanita Chee, Ian MacLeod, Jackie Nelson, Daniel Peach, Jennifer Huang, Dana Cook, Sam Hui, Stephanie Price, and Bryan Jackson.