Question

The heights of 9-year-old children are normally distributed, with a mean of 123 cm and a standard deviation of 10 cm. Find the probability that the mean height of three randomly selected 9-year-old children is greater than 125 cm

Answer 1

$P(X>125)$

for $X=125, Z=(125-123)/10$

Z=0.2

$\therefore P(X>125)=P(Z>0.2)$

$=1-0.5080$

$=0.492$