. 2014 Nov 14;16(11):e250. doi: 10.2196/jmir.3532

Table 2.

Correlations between tweets and sentinel-provided ILI^a rates.^b

	1. All tweets	2. Non-retweets	3. Retweets	4. Fisher’s z transformation^c	5. Tweets without a URL	6. Tweets with a URL	7. Fisher’s z transformation^d	8. Total number of tweets
	r	r	r	P	r	r	P
Boston	−.05	−.19	.08	<.001	.04	−.13	<.001	17,370
Chicago	.33	.50	.04	<.001	.49^e	.25	<.001	21,655
Cleveland	.63^e	.74^e	.42	<.001	.56^e	.55^e	.703	6632
Columbus	.01	.05	−.06	.019	−.04	.08	.001	3206
Denver	.76^e	.64^e	.74^e	<.001	.81^e	.63^e	<.001	5706
Detroit	.81^e	.84	.44	<.001	.62^e	.78^e	<.001	8417
Fort Worth	.69^e	.73^e	.45^e	<.001	.81^e	.62^e	<.001	4755
Nashville-Davidson	.77^e	.74^e	.54^e	<.001	.70^e	.66^e	<.001	5805
New York	.44^e	.42	.39	<.001	.32	.44	<.001	64,340
San Diego	.78^e	.73^e	.41^e	<.001	.69^e	.73^e	<.001	8002

^aILI: influenza-like illness

^bCorrelation coefficients of all tweets and tweet categories with sentinel-provided ILI rates for each city. Comparisons between tweets and ILI began in Weeks 36-49 (weeks starting September 1, 2013 to starting November 24, 2013) as ILI data became available by city and ended in Week 9 (ending March 1, 2014).

^cThis column displays the P values from Fisher’s z transformation comparing the correlation coefficients of non-retweets to retweets.

^dThis column displays the P values from Fisher’s z transformation comparing the correlation coefficients of tweets without a URL to tweets with a URL.

^eSignificant correlation coefficient (P<.05).