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CHAPTER 6. ANALYZING THE TALK.ABORTION NEWSGROUP 78
Figure 6.1: Comparison of Newspaper and Newsgroup Activity
4
3
Standardized Number of Contributions
2
1
0
−1
−2
−3
Newspaper Articles Dashed
kurtosis= 3.37
Newsgroup Messages Solid
kurtosis= 4.14
−4
0 50 100 150 200 250 300 350
Day
in the newsgroup, and the number of articles appearing in the newspaper index,
is presented in Figure 6.1. If the real-world events were responsible for the peaks
and valleys of activity in the newsgroup, the number of newspaper articles with
the word “abortion” on any given day, and the number of messages available in the
newsgroup would be correlated. This is not the case: in fact, the correlation coefficient
between the two measures is ;:15. Similarly, the correlation coefficient
between a newspaper articles lagged by three days, and the number of messages
in the newsgroup, is weakly and negatively correlated (r=;:09). Further, the trend
in the two indices are only weakly correlated. 4 It would appear that real-world
events, as measured by frequency of newspaper articles, had little impact on the
quantity of messages posted to the newsgroup.
The newsgroup is clearly more tractable than the newspaper, as indicated by the
greater kurtosis value associated with the its distribution. 5 Figure 6.1 indicates that
while the number of newspaper articles mentioning “abortion” appearing each day
4 The trend was calculated by subtracting the number of articles or messages appearing on Day
t2 from the number of articles appearing on Day t1. The correlation coefficient was :14.
5 Kurtosis measures the degree to which a distribution is prone to outliers. The kurtosis of a
normal distribution is 3; distributions with more outliers than normal distributions have kurtosis