The life expectancy (in hours) of a fluorescent tube is normally distributed with a mean 8000 and a standard deviation 1000. Find the probability that a tube lasts for more than 11000 hours.

Answer 1

Calculate Z as follows:
z=(x-μ)/σ
=(11000-8000)/1000
=3

From probability tables, find
P(Z>z).
P(Z>3)=1-P(Z<3)=1-0.99865=0.00135

Answer 2

The life expectancy of a fluorescent tube is normally distributed with a mean of 6, 800 hours and a standard deviation of 1,000 hours. Find the probability that a tube lasts for more than 8,800 hours.

Answer 3

8410

Answer 4

As a Senior High school student how much time do you spent in studying and answering the activities in your modules?Do you spend 25 hours in a week or more than that?Suppose that the average number of hours spent by Senior High school students in your school for their modular classes in a week is 25 hours with a standard deviation of 4 hours.Assuming that the study is true and the data is normally distributed,what is the probability that a random sample of 12 senior high school students spends more than 24 hours?