What is the standard deviation (sd) of the number of cardinal birds observed?

Ornithology

The Christmas Bird Count (CBC) is an annual tradition in Lexington, Massachusetts. A group of volunteers counts the number of birds of different species over a 1-day period. Each year, there are approximately 30€“35 hours of observation time split among multiple volunteers. The following counts were obtained for the Northern Cardinal (or cardinal, in brief) for the period 2005€“2011.

Table 5.9 Number of Cardinals observed Christmas Day, 2005€“2011, Lexington, Massachusetts

 

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Year Year Number Number 2005 2006 62 76 47 2009 69 2010 62 2007 63 53 2011 2008 Σ- Σ-27,212 Xi = 432, i=1" i=D1