Global warming is causing many species living on mountain slopes to shift their elevational ranges upward. Is the vertical extent of their ranges (the difference between the upper limit and the lower limit of their elevational range) also changing as ranges shift upward? To examine this, Freeman et al. (2018) surveyed birds on the Cerro de Pantiacolla in Peru in 2017 and compared their findings to a previous survey of the same mountain in 1985. The following numbers are changes in the vertical range extent of 14 mid-elevation bird species, in meters. A negative number indicates that the vertical extent of the range of that species has decreased, whereas a positive number indicates an increase; 0 indicates no change.

a. Test the null hypothesis that the mean change in the vertical extent of mountain birds is 0 meters (i.e., is neither increasing nor declining but is stable in the face of global warming).

b. What changes in the vertical extent of range are nevertheless consistent with the data? To answer, calculate the 95% confidence interval for the change in vertical range.

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100,100, 380,380, -100,-100, 0.0, -50, -50, -50, -150, -50, -50, -50, -150, 100,100, -50.-50.-200,-50, -50, -200, 50,50, 100 100