Given:
100 students:
pass = + 4
fail =+ 0
90 students passed: 90 * 4 = 360
10 students failed: 10 * 0 = 0
mean: 360 / 100 = 36
standard deviation:
36 - 4 = 32 ⇒ 32² = 1,024 * 90 = 92,160
36 - 0 = 36 ⇒ 36² = 1,296 * 10 = 12,960
92,160 + 12,960 = 105,120
105,120 / 100 = 1,051.20 ⇒ variance
Standard deviation = √1,051.20 = 32.42
Answer:
whats the question? please explain
Answer:
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
=
What an awesome question!