The exam scores are normally distributed with a mean \( \mu = 500 \) and standard deviation \( \sigma = 100 \).
Given: \( P(Z \leq 0.5) = 0.691 \)
We need to find: \( P(450 \leq X \leq 500) \)
Use the formula: $$ Z = \frac{X - \mu}{\sigma} $$
For \( X = 500 \): $$ Z = \frac{500 - 500}{100} = 0 $$ For \( X = 450 \): $$ Z = \frac{450 - 500}{100} = -0.5 $$
We calculate: $$ P(450 \leq X \leq 500) = P(-0.5 \leq Z \leq 0) = P(Z \leq 0) - P(Z \leq -0.5) $$
From symmetry: $$ P(Z \leq -0.5) = 1 - P(Z \leq 0.5) = 1 - 0.691 = 0.309 $$ and $$ P(Z \leq 0) = 0.5 $$
$$ P(-0.5 \leq Z \leq 0) = 0.5 - 0.309 = \boxed{0.191} $$
The probability that a randomly selected student scored between 450 and 500 is: 0.191
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Online Test Series, Information About Examination,
Syllabus, Notification
and More.