The time required to finish a test in normally distributed with a mean of 80 minutes and a standard
deviation of 15 minutes. What is the probability that a student chosen at random will finish the test in more
than 110 minutes?

Question

The time required to finish a test in normally distributed with a mean of 80 minutes and a standard
deviation of 15 minutes. What is the probability that a student chosen at random will finish the test in more
than 110 minutes?

anonymous · Answer

34%
	16%
	82%
	2%

anonymous · Answer

$$P(X>110)=P\left(\frac{X-80}{15}>\frac{110-80}{15}\right)=P(Z>2)$$

anonymous · Answer

If you're not familiar with $z$ tables and the computation of these sorts of probabilities, the other way to determine the value of $P(Z>2)$ is to ask - what proportion of a population lies 2 standard deviations away from the mean?|dw:1406080407791:dw|