Fig.3 Statistical power for sample counts in detecting the direction (fig. 3a) and magnitude (fig. 3b) of the population trend for a 10 years trend (on the left) and 20 years (on the right). The hashed line represents the threshold for statistical power (0.8). Trend variability between years and sectors is the one measured for ibex in GPNP (cvy=0.05, cvs=0.10) and statistical power is averaged between all the combinations of the other parameters.