Question 862984
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Hi
What is the standard error of the distribution of the sample mean? {{{5.5/sqrt(25)}}} = 1.1
 What proportion of the samples will have a mean useful life of more than 36 hours? 
normalcdf(36,100, 34,1.1) |100 a placeholder  0r P(z >2/1.1) = 3.45%
 What proportion of the sample will have a mean useful life greater than 33.5 hours? 
normalcdf(33.5,100, 34,1.1)  0r  P(z > -.5/1.1) = 67.53%
 What proportion of the sample will have a mean useful life between 33.5 and 36 hours? 
normalcdf(33.5,36, 34,1.1)  0r 67.53 - 3.45 = 64.08%
first are TI instructions(recommended) 'Or' is using z and z-calculator
Tables are fine.  Calculators quicker..so as one not loses there train of thought as to important concepts.