BBR did several measurements of actual IBUs as well as computing the estimates with various forulas.
Mark's Hefeweizen:
Extract, 1 oz Tettnang 4.5% @60mins
Avg of all the estimates: 15
StdD: 2
Rager: 17
Garetz 12 (Garetz always had the always lowest values)
Mosher 14
Tinseth 15
Daniels 17 (Daniels always had the highest values)
Actual measured IBUs: 7
Belgian Brunette
60 min .5 Styrian Goldings 6% and .85oz Hallertau 5.3%
Avg: 26
StD: 4
R: 30
G: 22
M: 23
T: 23
D: 30
Actual: 18
(Note: Beer was 6 months old)
Vanilla Porter
60min, 15 min, 5 min
Avg: 24
StD: 4.9
R: 27
G: 18
M: 23
T: 22
D: 31
Actual: 27
6pack Simcoe
15, 5 mins, flameout, dry-hop
Avg: 41
StD: 17.5
R: 37
G: 15
M: 42
T: 48
D: 63
Actual: 34
Late-hop Simcoe
Malt extract
10.1 minute boil
2.5 oz @15min, 1 @5, .5 @flameout, 1 oz Amarillo dry-hop
Avg: 38
StD: 19
R: 37
G: 10 (They corrected this later--18 after checking the numbers)
M: 38
T: 39
D: 64 (Corrected: 74)
Actual: 34
IPA
10 gal
18 oz cascade
2 @90 60 30 25 20 15 10 5 1
Avg: 85
StD: 21
R: 91
G: 57
M: 83
T: 78
D: 116
Actual: 77