The accompanying summary data on CeO₂ particle sizes (nm) under certain experimental conditions was read from a graph in the article "Nanoceria—Energetics of Surfaces, Interfaces and Water Adsorption" (J. of the Amer. Ceramic Soc., 2011: 3992-3999): 

  

      

  

a. What proportion of the observations are less than 5? 

  

b. What proportion of the observations are at least 6?

  

 c. Construct a histogram with relative frequency on the vertical axis and comment on interesting features. In particular, does the distribution of particle sizes appear to be reasonably symmetric or somewhat skewed? [Note: The investigators fit a lognormal distribution to the data; this is dis-cussed in Chapter 4.] 

  

d. Construct a histogram with density on the vertical axis and compare to the histogram in (c).

 

3.0-