Re:Apple Is Developing Its Own Screens for the First Time
by Retric on Monday March 19, 2018 @10:38AM
(#16618645)
This assumes each failure is independent. Often a single failure will cause many bad pixels on the same screen. So you might have 98 good screens 1 with one bad pixel and one with 5,000 bad pixels when the per pixel odds say you are going to end up with 1 good screen if you are lucky and 99 bad ones.
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Re:Apple Is Developing Its Own Screens for the First Time
by nonbel on Monday March 19, 2018 @04:40PM
(#16622931)
I simulated 100 screens with different numbers of pixels where the probability the first pixel is bad in a screen is p0 = 1e-6 and the presence of each bad pixel increases the probability of the next one by the same amount (ie probability for a second bad pixel is 2e-6 and for last pixel is p0*number_already_bad_px). A screen was accepted if it had 0 bad pixels. The results look pretty much the same:
num_pixels frac_accepted
1e+01 1.00
1e+02 1.00
1e+03 1.00
1e+04 0.98
1e+05 0.89
1e+06 0.32
1e+07 0.00
Of course this was just a convenient scheme to simulate. The greatest number of bad pixels was 86k for the 10 million px screen (so chance the last pixel was bad was ~9%). It does show that the independent pixel model isn't necessarily very far off though.
Re:Apple Is Developing Its Own Screens for the First Time
by Retric on Tuesday March 20, 2018 @11:08AM
(#16629188)
You messed up the math. You need to count (# number of pixels that where bad) / (total number of pixels produced) not simply call the odds for the first bad pixels as the rate of bad pixels.
Re:Apple Is Developing Its Own Screens for the First Time
by nonbel on Tuesday March 20, 2018 @05:16PM
(#16632747)
You are saying to adjust p0 so I get that the frequency of bad pixels = 1e-6? That makes sense but it would probably now depend on what size screens are being considered... not sure if I'll go back to it.