Question

Suppose exam scores are normally distributed with a mean of 70 and a standard deviation of 6. The probability that someone scores between a 70 and a 90 is?

Answer #1

Solution:

Given, the Normal distribution with,

= 70

= 6

Find P(Between 70 and 9)

= P(70< x< 90)

= P(X < 90) - P(X < 70)

= P[(X - )/ < (90 - 70)/6] - P[(X - )/ < (70 - 70)/6]

= P[Z < 3.33] - P[Z < 0.00]

= 0.9996 - 0.5000 ..Use z table

= 0.4996

**P(Between 70 and 9) = 0.4996**

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