In North America, between 100 million and 1 billion birds die each year by crashing into windows on buildings, more than any other human-related cause. This figure represents up to 5% of all birds in the area. One possible solution is to construct windows angled downward slightly so that they reflect the ground rather than an image of the sky to a flying bird. An experiment by Klem et al. (2004) compared the number of birds that died as a result of vertical windows, windows angled 20 degrees off vertical, and windows angled 40 degrees off vertical. The angles were randomly assigned with equal probability to six windows and changed daily; assume for this exercise that windows and window locations were identical in every respect except angle. Over the course of the experiment, 30 birds were killed by windows in the vertical orientation, 15 were killed by windows set at 20 degrees off vertical, and 8 were killed by windows set at 40 degrees off vertical. a. Clearly state an appropriate null hypothesis and an alternative hypothesis. b. What proportion of deaths occurred while the windows were set at a vertical orientation? c. What statistical test would you use to test the null hypothesis?
In North America, between 100 million and 1 billion birds die each year by crashing into windows on buildings, more than any other human-related cause. This figure represents up to 5% of all birds in the area. One possible solution is to construct windows angled downward slightly so that they reflect the ground rather than an image of the sky to a flying bird. An experiment by Klem et al. (2004) compared the number of birds that died as a result of vertical windows, windows angled 20 degrees off vertical, and windows angled 40 degrees off vertical. The angles were randomly assigned with equal
a. Clearly state an appropriate null hypothesis and an alternative hypothesis.
b. What proportion of deaths occurred while the windows were set at a vertical orientation?
c. What statistical test would you use to test the null hypothesis?
d. Carry out the statistical test from part (c). Is there evidence that window angle affects the mortality rates of birds? Show the data/calculations in a table and show work. Complete the calculation in R (commands and outputs).
e. Why were the windows assigned an angle at random? Why were they changed daily?
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