Refer to Exercise 8.5. Compute 10-year relative population change

8.7. Refer to Exercise 8.5. Compute 10-year relative population change y1 = (5.3 − 3.9)/3.9,
y2 = (7.2 − 5.3)/5.3, etc.
(a) Compute sample mean, median, and variance of the relative population change.
(b) Construct a time plot of the relative population change. What trend do you see now?
(c) Comparing the time plots in Exercises 8.6 and 8.7, what kind of correlation between
xi and yi would you expect? Verify by computing the sample correlation coefficient

What can you conclude? How would you explain this phenomenon?

a)        

Relative Population Mean =     0.2238

Relative population Median = 0.2097

Relative population variance = 0.0103

b) 

This plot basically show the relative rate of change in the population after each decade. It seems like the growth of the population is decreasing after each decade. This is not plotting the total number of the population, instead this plotting the relative rate of “increase of population”

c) While comparing the time plots in Exercises 8.6 and 8.7, I am expecting a negative correlation between xi and yi . Because if you look at the plot of 8.6, the value are increasing but the plot in example 8.7 show the value is decreasing.

Matlab gives me a negative value for correlation coefficient as expected =    -0.7884.