The average life span of a phone battery is 21 months with a standard deviation of 1 months. Assuming the battery life is normally distributed, what is the probability that a battery chosen at random will last more than 24 months?

Note: When finding Z-score round it to two decimal places and then use the Standard Normal Curve Table to find the area with four decimal places accuracy.

Round the answer to four decimal places.

Question

The average life span of a phone battery is 21 months with a standard deviation of 1 months. Assuming the battery life is normally distributed, what is the probability that a battery chosen at random will last more than 24 months?

Note: When finding Z-score round it to two decimal places and then use the Standard Normal Curve Table to find the area with four decimal places accuracy.

Round the answer to four decimal places.

anonymous · Answer

Let X be the randomly chosen battery, then since the battery life is normally distributed: 
$$P(X>24)=P({X-21 \over 1}>{24-21 \over 1})=P(Z>3)=P(Z<-3)$$

anonymous · Answer

Now use the table to find P(Z<-3), you will get:
P(Z<-3)=0.0013

anonymous · Answer

if your still on can you help me with this problem.... 
 

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