The Graph shows changes in the Consumer Price Index for the New York

Official Explanation

1. The average change in CPI over the year 2010 was approximately __________

The average change in CPI over the year 2010 can be calculated using the data points and online calculator. The monthly change in CPI values for 2010 fluctuated over a relatively small range. The change in CPI was 0% in February, September, November, and December, and 0.2% in January, April, May, August, and October. In March the CPI changed by 0.5%, in June by -0.1%, and in July by 0.1%. Use these values to find the average change:

\(\frac{1.0 +0.5}{12} = 0.125\)

Answer: B

2. The range of change in the CPI over the year 2011 was _______

The greatest percentage increase in the CPI in 2011 was 0.7% in March, and the greatest decline was –0.4% in December. The range of changes in the CPI over the year 2011 was 0.7 – (–0.4) = 1.1 percentage points.

Answer: E

The first impulse may be to find month-by-month differences and average those differences, but you can obtain the same result by finding the difference of the annual averages, and since one of these was already calculated for an earlier question, that will be the more efficient path. The average change in CPI in 2010, determined in problem 358, was 0.125. Find the average CPI for 2011:

\(\frac{0.3+0.5+0.7+0.4+0.6+0.2+0.3+0.4+0.2-0.2+0.3+0.4}{12} = \frac{2.7}{12} = 0.225\)

Answer: B