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CASE POSITIVITY IN FL I wanted to focus on 2 Qs I've gotten recently
The diff in the 2 measures reported by FL result from excluding previous + for 1 of the measures. What % are excluded?The weekly report removes repeat testers w/i the week. What's the impact?1/
Quick review:
MEASURE 1: case positivity
- numerator: unique people who test +
- denominator: unique people tested
MEASURE 2: % positivity for new cases
- same calculation but exclude (from numerator and denominator) anyone who tested + prior to the date being assessed.
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MEASURE 1: case positivity
- numerator: unique people who test +
- denominator: unique people tested
MEASURE 2: % positivity for new cases
- same calculation but exclude (from numerator and denominator) anyone who tested + prior to the date being assessed.
2/
To understand diff in the measures, I focused on the % excluded from the numerator and denominator of MEASURE 2.
I used data from 9/27 thru 10/3, as listed on the 10/4 state and county reports.
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I used data from 9/27 thru 10/3, as listed on the 10/4 state and county reports.
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The % removed from the NUMERATOR (+ people who previously tested +) was 29.6% for the week
- daily % removed varied from 26.7% to 32.4%
The % removed from the DENOMINATOR (+/- people who previously tested +) was 8.1% for the week
- daily % removed varied from 7.7% to 8.8%
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- daily % removed varied from 26.7% to 32.4%
The % removed from the DENOMINATOR (+/- people who previously tested +) was 8.1% for the week
- daily % removed varied from 7.7% to 8.8%
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So, a higher % of people who tested + are being removed from the numerator (about 1 in 3) than the % of people tested from the denominator (about 1 in 12).
That's why the % positivity for new cases is LOWER than the case positivity.
What about the WEEKLY TESTING REPORT?
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That's why the % positivity for new cases is LOWER than the case positivity.
What about the WEEKLY TESTING REPORT?
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Around 60-65% of people tested daily in FL have been tested previously.
So, we tend to see a lot of repeat testers in the daily positivity measures (both of them).
Florida releases ONE DATASET weekly that de-duplicates people tested during a given week.
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So, we tend to see a lot of repeat testers in the daily positivity measures (both of them).
Florida releases ONE DATASET weekly that de-duplicates people tested during a given week.
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This report gives numerator and denominator for the "% positivity for new cases" (MEASURE #2).
If one were to ADD the daily numerators and denominators from the week, they would calculate:
- 16,191 / 365,705 = 4.43%
The weekly report calculates:
- 16,191 / 347,123 = 4.66%
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If one were to ADD the daily numerators and denominators from the week, they would calculate:
- 16,191 / 365,705 = 4.43%
The weekly report calculates:
- 16,191 / 347,123 = 4.66%
7/
The NUMERATORS are the same, which makes sense.
As soon as a person tests +, they are not included in any subsequent day's calculations (for this positivity measure).
In that sense, the numerator of the "% positivity for new cases" is always de-duplicated, even daily.
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As soon as a person tests +, they are not included in any subsequent day's calculations (for this positivity measure).
In that sense, the numerator of the "% positivity for new cases" is always de-duplicated, even daily.
8/
But the DENOMINATORS are different since DOH de-duplicates:
- people who tested negative multiple days in the week
- people who tested negative and then positive during the week
How much did de-duplication remove?
- 18,582 of 365,705 (or 5.1%) of the denominator
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- people who tested negative multiple days in the week
- people who tested negative and then positive during the week
How much did de-duplication remove?
- 18,582 of 365,705 (or 5.1%) of the denominator
9/
So, would seem that, if this week is representative of most weeks recently:
- about 1 in 20 who are tested in FL are being tested multiple times WITHIN A 7-DAY PERIOD
Also, the % positivity from the weekly rpt tends to be
than the daily avg due to removal of repeat neg.
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- about 1 in 20 who are tested in FL are being tested multiple times WITHIN A 7-DAY PERIOD
Also, the % positivity from the weekly rpt tends to be
than the daily avg due to removal of repeat neg.10/
Last, just a "where are we now" regarding TRENDS in these two measures (red and pink lines) and the ratio of new cases to newly tested (blue line)... (ON LEFT)
...and the daily numbers since Sept 1 (ON RIGHT)
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...and the daily numbers since Sept 1 (ON RIGHT)
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