- #1
Dell
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the nationwide results of a math exam have a normal distribution, with an average of 68 and a standard deviation of 12.57.
100 students were randomly selected,
what is the probability that at least 50 of them will have achieved more that 70 in the exam?
A--> the mark of the chosen 100
A~N(68, 1.257)
P(A>70)=1-P(A<70)=0.9441 (from a standard Z table)
T~B(100,0.9441) ---> X~NB(94.41,2.297)
P(X>50)=1-P(X<50)=~ 1
is this correct?
the answer in my book says 0.0838, but since the average is 68, that doesn't seem likely to me,
100 students were randomly selected,
what is the probability that at least 50 of them will have achieved more that 70 in the exam?
A--> the mark of the chosen 100
A~N(68, 1.257)
P(A>70)=1-P(A<70)=0.9441 (from a standard Z table)
T~B(100,0.9441) ---> X~NB(94.41,2.297)
P(X>50)=1-P(X<50)=~ 1
is this correct?
the answer in my book says 0.0838, but since the average is 68, that doesn't seem likely to me,