Figure - PMC

Skip to main content

An official website of the United States government

Here's how you know

Here's how you know

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

View full-text article in PMC

. 2011 Apr 27;6(4):e18687. doi: 10.1371/journal.pone.0018687

Search in PMC
Search in PubMed
View in NLM Catalog
Add to search

This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

This is an open-access article distributed under the terms of the Creative Commons Public Domain declaration, which stipulates that, once placed in the public domain, this work may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose.

PMC Copyright notice

1. Data Sources: a. US Influenza Virologic Surveillance System (http://www.cdc.gov/flu/weekly/fluactivity.htm); and b. Google Flu Trends (http://www.google.org/about/flutrends/us-historic.txt). 2. There are 166 total observations in each panel. Influential observations were defined by DFBETA statistic greater than the absolute value of 2 divided by the square root of the total number of observations in a simple linear regression model [17]. 3. R_A represents Pearson's correlation coefficients calculated from comparisons of Google Flu Trends with US Influenza Virologic Surveillance. 4. R'_A represents the calculated Pearson's correlation coefficients after exclusion of all influential observations. 5. Because CDC surveillance is intensified from calendar week 40 through calendar week 20 of the subsequent year, we restricted our correlation analyses to this time period.