a. Draw a scatter plot of these data. Which variable should be the explanatory variable (X), and which should be the response variable (Y)? b. What is the rate of change in the number of plant species supported per nutrient type added? Pro- vide a standard error for your estimate. c. Add the least squares regression line to your inscatter plot. What fraction of the variation in the number of plant species is "explained" by the number of nutrients added? d. Test the null hypothesis of no treatment effect on the number of plant species.20. You might think that increasing the nutrient resources available would elevate the number of plant species that an area could support, but the evidence suggests otherwise. The data in the accompanying table are from the Park Grass Experiment at Rothamsted Experimental Station in the U.K., where grassland field plots have been fertilized annually for the past 150 years (collated by Harpole and Tilman 2007). The number of plant species recorded in 10 plots is given in response to the number of different nutrient types added in the fertilizer treatment (nutrient types include nitrogen, phosphorus, potassium, and so on). no Number of Number of Plot nutrients added plant species 36 OO 36 0 32 34 33 DO YOU A WN WHWNA 30 20 23 9 21 10 4 16