Question

7.46 More on global warming. Side-by-side boxplots offer a different look at the data. Group the data into peri- ods of roughly equal length: 1917-1941, 1942-1966, 1967-1991, and 1992-2015. Make boxplots to compare ice breakup dates in these four time periods. Write a brief description of what the plots show.

Answer 1

The given data is to be plotted as a box plot. A box plot depicts the spread of the data. Specifically it summarizes the data using a four number summary. These are the minimum, maximum, first quartile. and third quartile. The box plot has a box that ranges between first and third quartiles and has whiskers that extend from the first quartile to minimum, and from third quartile to maximum.

Therefore, in order to draw a box plot for each of the categories, we first divide the data into categories as mentioned and the calculate these four parameters for each of the groups. Doing so, we get:

	Min	First Quartile	Second Quartile	Max
1917-1941	1	12	22	26
1942-1966	9	13	20	31
1967-1991	5	11	19	23
1992-2015	1	6.75	14.5	31

Next we draw a box plot for the four groups:

Box Plot 40 30 20 Days 10 0 1917-1941 1942-1966 1967-1991 1992-2015 Years

As can seen from the bo plots, all the four groups depict a large amount of overlap and hence the number of ice breakup dates in these four periods are more or less the same. However, there seems to be a decreasing trend with the majority of the breakup dates being lowest for 1992-2015 period. Additionally, we can also see that the variation in the data is the larges for the 1992-2015 period.

asdfa