The exam scores are normally distributed with a mean μ=500 and standard deviation σ=100.
Given: P(Z≤0.5)=0.691
We need to find: P(450≤X≤500)
Use the formula: Z=X−μσ
For X=500: Z=500−500100=0 For X=450: Z=450−500100=−0.5
We calculate: P(450≤X≤500)=P(−0.5≤Z≤0)=P(Z≤0)−P(Z≤−0.5)
From symmetry: P(Z≤−0.5)=1−P(Z≤0.5)=1−0.691=0.309 and P(Z≤0)=0.5
P(−0.5≤Z≤0)=0.5−0.309=0.191
The probability that a randomly selected student scored between 450 and 500 is: 0.191
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