What is the expected mean number of failures?
2007-07-22 07:21:47 · 5 answers · asked by Anonymous in Science & Mathematics ➔ Mathematics
I would like to comment on the answers above. Of course you can't have 221.25 people fail the exam. However, this is a particular number of people that we are talking about; this is the mean of all of the possible counts of failures. We know that the mean of a data set does not have to be one of the values in a data set. So 221.25 is perfectly acceptable as the mean. It doesn't need to be rounded.
I think it is careless for you guys to assume that you have to round this to a whole number. If you were to use the normal approxmation on this, you would use a mean of 221.25. Rounding it to 221 or 222 would lead to errors in calculating probabilities. Be more careful guys!
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The answer:
Since 41% pass the exam, then 100-41 = 59% fail. The number of people who will fail the exam will have a binomial distribution with number of trials n = 375 and probability of success p = 0.59. The mean of the binomial is np, so this makes the mean
np = 375*0.59 = 221.25 EXACTLY! DO NOT ROUND THIS!
2007-07-22 07:39:28 · answer #1 · answered by blahb31 6 · 1⤊ 1⤋
If 41% is the probability of passing, 59% is the probability of failing and that multiplied by the number of students will give the desired answer. 221.25 is the value and since a non-integer cannot be there, 221 is the answer.
2007-07-22 14:28:01 · answer #2 · answered by Swamy 7 · 0⤊ 1⤋
soo 100-41=59 so 59% dont pass
59 x
--- = ----
100 375
cross multiplaction
59*375=100x
22125=100x
----------------
100
221.25=x
since u cant have 1/4 of a person 222 people fail it
good luck
2007-07-22 14:33:48 · answer #3 · answered by Mae-Day 3 · 0⤊ 1⤋
222
2007-07-22 14:27:30 · answer #4 · answered by Natalie 2 · 0⤊ 1⤋
59% FAIL.
.59*375= 221.25 FAIL
2007-07-22 15:37:29 · answer #5 · answered by CoolioMADDog 4 · 0⤊ 0⤋