SOLUTION: A statistical analysis of 1,000 long distance telephone calls made from the headquarters of a corporation indicates that the length of these calls is normally distributed with a me

Question 841806: A statistical analysis of 1,000 long distance telephone calls made from the headquarters of a corporation indicates that the length of these calls is normally distributed with a mean of 240 seconds and standard deviation of 40 seconds.
What is the probability that a particular call lasted between 110 and 180 seconds?
How many of the calls lasted less than 180 seconds or more than 300 seconds?
Answer by ewatrrr(24785) (Show Source): You can put this solution on YOUR website!

 

Hi,

Using TI:

*Note: 

probability that a particular call lasted between 110 and 180 seconds? 

P(110>x<180) 

Find z:

  z = (110-240)/1.27 = -130/1.27

  z = (180-240)/1.27 = -60/1.27

P(between smaller z and larger z): The syntax is normalcdf(smaller z, larger z).

normalcdf(-130/1.27, -60/1.27)



How many of the calls lasted less than 180 seconds or more than 300 seconds

 1000(1 - normalcdf(-60/1.27, 60/1.27))

 

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