Question 1182574
Ho: mu=1000 hours
Ha: mu NE 1000 hours
alpha=0.05 P{reject Ho|Ho true}
test is a z.
critical value is |z| >1.96
calculation z=(990-1000)/80/sqrt(40)
=-10*sqrt(40)/80
=-0.79 
fail to rect Ho, The mean lifetime can be 1000 hours; insufficient evidence to state otherwise.
p-value=0.43