Question 879653
Population: mean = 1260, sd = 140, sample of 100
*Note: {{{z =blue (x - mu)/blue(sigma/sqrt(n))}}}
z = 40/(140/sqrt(100)) = 40/14 = 2.8574
P(x>=1300)= 1 - P(z<1300) = .0021  0r .21%
E = .0021*100 = .21 bulbs , basically none