<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE article PUBLIC "-//NLM//DTD Journal Publishing DTD v2.0 20040830//EN" "http://dtd.nlm.nih.gov/publishing/2.0/journalpublishing.dtd">
<article xmlns:xlink="http://www.w3.org/1999/xlink" article-type="correction" dtd-version="2.0">
  <front>
    <journal-meta>
      <journal-id journal-id-type="publisher-id">JPH</journal-id>
      <journal-id journal-id-type="nlm-ta">JMIR Public Health Surveill</journal-id>
      <journal-title>JMIR Public Health and Surveillance</journal-title>
      <issn pub-type="epub">2369-2960</issn>
      <publisher>
        <publisher-name>JMIR Publications</publisher-name>
        <publisher-loc>Toronto, Canada</publisher-loc>
      </publisher>
    </journal-meta>
    <article-meta>
      <article-id pub-id-type="publisher-id">v7i4e30017</article-id>
      <article-id pub-id-type="pmid">33929969</article-id>
      <article-id pub-id-type="doi">10.2196/30017</article-id>
      <article-categories>
        <subj-group subj-group-type="heading">
          <subject>Corrigenda and Addenda</subject>
        </subj-group>
        <subj-group subj-group-type="article-type">
          <subject>Corrigenda and Addenda</subject>
        </subj-group>
      </article-categories>
      <title-group>
        <article-title>Correction: Predicting Age Groups of Reddit Users Based on Posting Behavior and Metadata: Classification Model Development and Validation</article-title>
      </title-group>
      <contrib-group>
        <contrib id="contrib1" contrib-type="author" corresp="yes">
          <name name-style="western">
            <surname>Chew</surname>
            <given-names>Robert</given-names>
          </name>
          <degrees>MSc</degrees>
          <xref rid="aff1" ref-type="aff">1</xref>
          <address>
            <institution>Center for Data Science</institution>
            <institution>RTI International</institution>
            <addr-line>3040 East Cornwallis Road</addr-line>
            <addr-line>Research Triangle Park, NC, 27709</addr-line>
            <country>United States</country>
            <phone>1 9195415823</phone>
            <email>rchew@rti.org</email>
          </address>
          <ext-link ext-link-type="orcid">https://orcid.org/0000-0002-6979-1766</ext-link>
        </contrib>
        <contrib id="contrib2" contrib-type="author">
          <name name-style="western">
            <surname>Kery</surname>
            <given-names>Caroline</given-names>
          </name>
          <degrees>MSc</degrees>
          <xref rid="aff1" ref-type="aff">1</xref>
          <ext-link ext-link-type="orcid">https://orcid.org/0000-0002-1794-3369</ext-link>
        </contrib>
        <contrib id="contrib3" contrib-type="author">
          <name name-style="western">
            <surname>Baum</surname>
            <given-names>Laura</given-names>
          </name>
          <degrees>MA, MPH</degrees>
          <xref rid="aff2" ref-type="aff">2</xref>
          <ext-link ext-link-type="orcid">https://orcid.org/0000-0002-4982-9149</ext-link>
        </contrib>
        <contrib id="contrib4" contrib-type="author">
          <name name-style="western">
            <surname>Bukowski</surname>
            <given-names>Thomas</given-names>
          </name>
          <degrees>MA, MPA</degrees>
          <xref rid="aff3" ref-type="aff">3</xref>
          <ext-link ext-link-type="orcid">https://orcid.org/0000-0001-5720-8564</ext-link>
        </contrib>
        <contrib id="contrib5" contrib-type="author">
          <name name-style="western">
            <surname>Kim</surname>
            <given-names>Annice</given-names>
          </name>
          <degrees>PhD</degrees>
          <xref rid="aff4" ref-type="aff">4</xref>
          <ext-link ext-link-type="orcid">https://orcid.org/0000-0001-6585-5876</ext-link>
        </contrib>
        <contrib id="contrib6" contrib-type="author">
          <name name-style="western">
            <surname>Navarro</surname>
            <given-names>Mario</given-names>
          </name>
          <degrees>PhD</degrees>
          <xref rid="aff5" ref-type="aff">5</xref>
          <ext-link ext-link-type="orcid">https://orcid.org/0000-0002-1029-2209</ext-link>
        </contrib>
      </contrib-group>
      <aff id="aff1">
        <label>1</label>
        <institution>Center for Data Science</institution>
        <institution>RTI International</institution>
        <addr-line>Research Triangle Park, NC</addr-line>
        <country>United States</country>
      </aff>
      <aff id="aff2">
        <label>2</label>
        <institution>Center for Health Analytics, Media, and Policy</institution>
        <institution>RTI International</institution>
        <addr-line>Atlanta, GA</addr-line>
        <country>United States</country>
      </aff>
      <aff id="aff3">
        <label>3</label>
        <institution>Center for Health Analytics, Media, and Policy</institution>
        <institution>RTI International</institution>
        <addr-line>Berkeley, CA</addr-line>
        <country>United States</country>
      </aff>
      <aff id="aff4">
        <label>4</label>
        <institution>Center for Health Analytics, Media, and Policy</institution>
        <institution>RTI International</institution>
        <addr-line>Research Triangle Park, NC</addr-line>
        <country>United States</country>
      </aff>
      <aff id="aff5">
        <label>5</label>
        <institution>Office of Health Communications and Education</institution>
        <institution>Center for Tobacco Products</institution>
        <institution>US Food and Drug Administration</institution>
        <addr-line>Silver Spring, MD</addr-line>
        <country>United States</country>
      </aff>
      <author-notes>
        <corresp>Corresponding Author: Robert Chew 
        <email>rchew@rti.org</email></corresp>
      </author-notes>
      <pub-date pub-type="collection">
        <month>4</month>
        <year>2021</year>
      </pub-date>
      <pub-date pub-type="epub">
        <day>30</day>
        <month>4</month>
        <year>2021</year>
      </pub-date>
      <volume>7</volume>
      <issue>4</issue>
      <elocation-id>e30017</elocation-id>
      <history>
        <date date-type="received">
          <day>28</day>
          <month>4</month>
          <year>2021</year>
        </date>
        <date date-type="accepted">
          <day>28</day>
          <month>4</month>
          <year>2021</year>
        </date>
      </history>
      <copyright-statement>©Robert Chew, Caroline Kery, Laura Baum, Thomas Bukowski, Annice Kim, Mario Navarro. Originally published in JMIR Public Health and Surveillance (https://publichealth.jmir.org), 30.04.2021.</copyright-statement>
      <copyright-year>2021</copyright-year>
      <license license-type="open-access" xlink:href="https://creativecommons.org/licenses/by/4.0/">
        <p>This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in JMIR Public Health and Surveillance, is properly cited. The complete bibliographic information, a link to the original publication on https://publichealth.jmir.org, as well as this copyright and license information must be included.</p>
      </license>
      <self-uri xlink:href="https://publichealth.jmir.org/2021/4/e30017" xlink:type="simple"/>
      <related-article related-article-type="corrected-article" id="v7i3e25807" ext-link-type="doi" xlink:href="10.2196/mhealth.25807" vol="7" page="e25807" xlink:type="simple">https://publichealth.jmir.org/2021/3/e25807</related-article>
    </article-meta>
  </front>
  <body>
    <p>In “Predicting Age Groups of Reddit Users Based on Posting Behavior and Metadata: Classification Model Development and Validation” (JMIR Public Health Surveill 2021;7(3):e25807) the authors noted one error.</p>
    <p>In the originally published manuscript, one sentence under the “Principal Findings” section was incorrect. The following sentence appeared in the second paragraph of this section:</p>
    <disp-quote>
      <p>The adult age group tended to have shorter comments than the adult age group.</p>
    </disp-quote>
    <p>In the corrected version of the manuscript, this sentence has been changed to:</p>
    <disp-quote>
      <p>The adolescent age group tended to have shorter comments than the adult age group.</p>
    </disp-quote>
    <p>The correction will appear in the online version of the paper on the JMIR Publications website on April 30, 2021, together with the publication of this correction notice. Because this was made after submission to PubMed, PubMed Central, and other full-text repositories, the corrected article has also been resubmitted to those repositories.</p>
  </body>
</article>
