Certain tubes manufactured by a company have a mean lifetime of 800 hours and a standard deviation of 60 hours. Find the probability that a random sample of 16 tubes taken from the group will have a mean lifetime (a) between 790 and 810 hours, (b) less than 785 hours, (c) more than 820 hours, (d) between 770 and 830 hours

Step-by-step explanation:

given that certain tubes manufactured by a company have a mean lifetime of 800 hours and a standard deviation of 60 hours.

Sample size n =16

Std error of sample mean =

x bar follows N(800, 15)

the probability that a random sample of 16 tubes taken from the group will have a mean lifetime

(a) between 790 and 810 hours,

=

(b) less than 785 hours

, (c) more than 820 hours,

(d) between 770 and 830 hours

=

+25 = x

step-by-step explanation:

here x is the hypotenuse of a right triangle whose legs are 7 and 24.   by the pythagorean theorem, 7² + 24² must equal x²:

x² = 49 + 576 = 625.   thus, x = +√625 = +25 = x

80 the answer is 80

step-by-step explanation: