If you are right 85% of the time, what is the probabilty of being wrong at least 1 time out of the next 7?
If someone can please tell me how to do it? This has been the only part of the entire book i havent been able to understand! :(
Thanks
2007-12-16 09:57:46 · 4 answers · asked by Epiphany 6 in Science & Mathematics ➔ Mathematics
You are right 85% of the time, so assuming you are right on all 7 times
(0.85)^7= .32
Since total probability is = 1,
1-0.32 =.68 * 100% = ~68% of getting at least 1 wrong
2007-12-16 10:01:08 · answer #1 · answered by ¿ /\/ 馬 ? 7 · 2⤊ 0⤋
All possible outcomes of 7 responses can be divided into the following two groups:
1) You are correct every single time, and
2) You are incorrect at least once.
As this is an exhaustive list (includes all possible outcomes), the probabilities of these two outcomes must add up to one.
So the probability of being incorrect at least once = 1 - Pr (being correct every time)
= 1 - 0.85^7 = 0.679 (3 dp) or 67.9%
2007-12-16 10:04:09 · answer #2 · answered by ozperp 4 · 1⤊ 0⤋
Figure out the probability of being right 7 times in a row, and then subtract from 100%.
2007-12-16 10:01:23 · answer #3 · answered by railbird 3 · 0⤊ 0⤋
Wow! I didn't realise there were so many clever people on YA....Respect
2007-12-19 09:30:21 · answer #4 · answered by Anonymous · 0⤊ 0⤋