1. in north america many birds die because they collide with windows of high-rise buildings one possible solution to resolve the problem is to construct windows angled down slightly toward the ground, so that they reflect the ground rather than an image of the sky to flying bird. an experiment compared the number of birds that died as a result of vertical windows windows angled 20 of vertical and windows angled 40° off vertical. the angles were randomly assigned with equal probability to six windows and changed daily. window shape, color and other external characteristics were kept identical. window locations matched the same location characteristics in terms of ground and sky . what other conditions need to be kept identical in this experiment to avoid influencing the results? over the course of the experiment 30 birds were killed by windows in the vertical orientation, 15 were killed by windows set at 20° off vertical and 8 birds were killed by windows set at 40° of vertical. do the data support the assumption that window angles relative to the vertical affect bird death rates as a result of collision with a window of a high-rise building?