Complex effect size conversion - Meta-Analysis Resources2022-01-21T08:07:59Zhttps://meta-analysis.ning.com/forum/topics/complex-effect-size-conversion?groupUrl=EScalcs&feed=yes&xn_auth=noRight, it cannot be calculate…tag:meta-analysis.ning.com,2014-06-09:5367515:Comment:206372014-06-09T18:55:26.010ZBlair T. Johnsonhttps://meta-analysis.ning.com/profile/BlairTJohnson
<p>Right, it cannot be calculated with the zero cell. When I calculate the OR using dstat 2, I come up with the same OR (and implied variance). This OR of 0.0034 converts to an SMD of 3.278, and a 95% CI of 2.61 to 3.95, so the underlying variance still implies a fairly wide CI. These are extremely large effects that you are documenting. You should see that your variance estimates get smaller with larger studies, so then the logic is correct. I see no mistake. You should go with the…</p>
<p>Right, it cannot be calculated with the zero cell. When I calculate the OR using dstat 2, I come up with the same OR (and implied variance). This OR of 0.0034 converts to an SMD of 3.278, and a 95% CI of 2.61 to 3.95, so the underlying variance still implies a fairly wide CI. These are extremely large effects that you are documenting. You should see that your variance estimates get smaller with larger studies, so then the logic is correct. I see no mistake. You should go with the Haldane-corrected version!</p> I realize that I was probably…tag:meta-analysis.ning.com,2014-06-06:5367515:Comment:206352014-06-06T18:28:06.575ZEmilie Champagnehttps://meta-analysis.ning.com/profile/EmilieChampagne
<p>I realize that I was probably doing the correction wrong, so finally, it might be okay (great!).Just to help anyone who would find this post, here's an exemple:</p>
<p>My data are percentage plant individual browsed by herbivore with or without treatment, so I usually have to <strong><em>create</em></strong> the 2 x2 table. For that, you need to know the n in each cell.</p>
<p> Events (browsed) Non-events (unbrowsed)</p>
<p>Treatment …</p>
<p>I realize that I was probably doing the correction wrong, so finally, it might be okay (great!).Just to help anyone who would find this post, here's an exemple:</p>
<p>My data are percentage plant individual browsed by herbivore with or without treatment, so I usually have to <strong><em>create</em></strong> the 2 x2 table. For that, you need to know the n in each cell.</p>
<p> Events (browsed) Non-events (unbrowsed)</p>
<p>Treatment 0 40</p>
<p>Control 30 10</p>
<p>Without correction: OR = (0 * 10) / (30 * 40) = 0 and it's V = infinite</p>
<p>With correction: OR = ((0 + 0.5)*(10+0.5)/((30+0.5)*(40+0.5)) = 0.004 and it's v = 2.15</p>
<p>and then I would transform it to a LogOR.</p>
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<p>Thanks Blair for the help. If you see any mistake in what I've done, please let me know.</p> Can you give me an example 2…tag:meta-analysis.ning.com,2014-06-06:5367515:Comment:202882014-06-06T16:37:54.788ZBlair T. Johnsonhttps://meta-analysis.ning.com/profile/BlairTJohnson
<p>Can you give me an example 2 x 2 table that exhibits the problem?</p>
<p>Can you give me an example 2 x 2 table that exhibits the problem?</p> Thanks. I tried it (partially…tag:meta-analysis.ning.com,2014-06-06:5367515:Comment:202872014-06-06T13:11:14.421ZEmilie Champagnehttps://meta-analysis.ning.com/profile/EmilieChampagne
<p>Thanks. I tried it (partially for the moment), but it still greatly increase the variance and bring the weight to 0. I wished their would be something else to do.</p>
<p>I read a bit about the Peto method, that estimate OR differently and can handle 0, but from what I've read, it's a different way of doing the entire meta-analysis and it doesn't seem to fit with effect size conversion or meta-regression...</p>
<p>Thanks. I tried it (partially for the moment), but it still greatly increase the variance and bring the weight to 0. I wished their would be something else to do.</p>
<p>I read a bit about the Peto method, that estimate OR differently and can handle 0, but from what I've read, it's a different way of doing the entire meta-analysis and it doesn't seem to fit with effect size conversion or meta-regression...</p> Oh, I see. There is something…tag:meta-analysis.ning.com,2014-06-05:5367515:Comment:204692014-06-05T16:28:16.766ZBlair T. Johnsonhttps://meta-analysis.ning.com/profile/BlairTJohnson
<p>Oh, I see. There is something called the Haldane Correction to solve the problem. Essentially you add 0.5 to each cell frequency, and that gets rid of the zero n problem. Here's <a href="http://www.statsdirect.com/help/default.htm#chi_square_tests/haldane_correction.htm" target="_blank">a link</a> describing it.</p>
<p>Oh, I see. There is something called the Haldane Correction to solve the problem. Essentially you add 0.5 to each cell frequency, and that gets rid of the zero n problem. Here's <a href="http://www.statsdirect.com/help/default.htm#chi_square_tests/haldane_correction.htm" target="_blank">a link</a> describing it.</p> Sorry, I was unclear. Some of…tag:meta-analysis.ning.com,2014-06-05:5367515:Comment:206312014-06-05T15:01:53.962ZEmilie Champagnehttps://meta-analysis.ning.com/profile/EmilieChampagne
<p>Sorry, I was unclear. Some of the data used to compute the OR are 0. So if I refer to the Borenstein nomenclature for the equation :</p>
<p>Table 5.1 Nomenclature for 2 2 table of outcome by treatment.<br/> Events Non-Events N<br/>Treated A B n 1<br/>Control C D n 2</p>
<p>One of my event or non-event (A,B,C or D) is 0.</p>
<p>Sorry, I was unclear. Some of the data used to compute the OR are 0. So if I refer to the Borenstein nomenclature for the equation :</p>
<p>Table 5.1 Nomenclature for 2 2 table of outcome by treatment.<br/> Events Non-Events N<br/>Treated A B n 1<br/>Control C D n 2</p>
<p>One of my event or non-event (A,B,C or D) is 0.</p> I thought that with ORs, 0 is…tag:meta-analysis.ning.com,2014-06-05:5367515:Comment:202842014-06-05T14:57:52.434ZBlair T. Johnsonhttps://meta-analysis.ning.com/profile/BlairTJohnson
<p>I thought that with ORs, 0 is infinity so it cannot appear. Yes, an OR of 0 would be astronomical in size! How is it possible that a report would give a zero for an OR, unless it is a typographical error? (Rounding?)</p>
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<p>I thought that with ORs, 0 is infinity so it cannot appear. Yes, an OR of 0 would be astronomical in size! How is it possible that a report would give a zero for an OR, unless it is a typographical error? (Rounding?)</p>
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