Question

The lifespan of a fluorescent lamp used in greenhouses is normally distributed (Gauss) with an average...

The lifespan of a fluorescent lamp used in greenhouses is normally distributed (Gauss) with an average of 600 hours and a standard deviation of 40 hours.
a) Calculate the probability that a randomly chosen lamp has a lifespan greater than 695 hours,
b) What times of last life are within the 85th percentile?
c) How long will 30% of the lamps last for the longest?
d) How long will 30% of the lamps last less time?
Ans.
a) 0.0087,
b) 641.6 hrs maximum,
c) 620.8 hrs minimum,
d) 579.2 hrs maximum

Homework Answers

Answer #1

Mean, = 600 hours

SD, = 40 hours

Let X denote the lifespan of a flourescent lamp

(a) The probability that a randomly chosen lamp has a lifespan greater than 695 hours = P(X > 695)

= P{Z > (695 - 600)/40}

= P(Z > 2.375)

= 0.0088

(b) Corresponding to 85th percentile, the z value is 1.0365

Thus the last life = 600 + 1.0365*40 = 641.46 hrs maximum

(c) Corresponding to 30% of the lamps with longest life, the z value = 0.5245

Thus the required life = 600 + 0.5245*40 = 620.98 hrs minimum

(d) Corresponding to 30% of the lamps with least time, the z value = -0.5245

Thus the required life = 600 + (-0.5245)*40 = 579.02 hrs maximum

Know the answer?
Your Answer:

Post as a guest

Your Name:

What's your source?

Earn Coins

Coins can be redeemed for fabulous gifts.

Not the answer you're looking for?
Ask your own homework help question
Similar Questions
one-hundred random chosen lamps lifetime are measured. mean = 1320, SD=180 (units = hours). a. If...
one-hundred random chosen lamps lifetime are measured. mean = 1320, SD=180 (units = hours). a. If "A" represents sample mean of the lifetime of one-hundred lamps measured in given units, what is the expected value of "A" and the SD of "A"? b. if units were instead = days and not hrs, how would answer for question "a." change (both mean and SD)? c. what is probabiltiy that sample mean is b/w one-thousand-three-hundred and one-thousand-three-hundred-fifty hrs...using central limit theorem? d,if...
The lifespan of a fruit fly is normally distributed with an average of 40 days and...
The lifespan of a fruit fly is normally distributed with an average of 40 days and a standard deviation of 7.4 days. a) What is the probability that a randomly selected fruit fly lives longer than 50 days? b) If a fruit fly lives longer than 75% of all other fruit flies, how long did it live? 1 c) If we take a sample of 80 fruit flies, what is the probability the sample mean is within 1 day of...
The number of chocolate chips in a bag of chocolate chip cookies is approximately normally distributed...
The number of chocolate chips in a bag of chocolate chip cookies is approximately normally distributed with a mean of 1262 chips and a standard deviation of 118 chips. A. About how many percent of the cookie bags are in between 1200 and 1300 chips. B. Determine the 30th percentile for the number of chocolate chips in a bag. C. Determine the minimum number of chocolate chips in a bag that make up the middle 95 % of bags. D....
1. Suppose that the time it takes you to drive to work is a normally distributed...
1. Suppose that the time it takes you to drive to work is a normally distributed random variable with a mean of 20 minutes and a standard deviation of 4 minutes. a. the probability that a randomly selected trip to work will take more than 30 minutes equals: (5 pts) b. the expected value of the time it takes you to get to work is: (4 pts) c. If you start work at 8am, what time should you leave your...
You are asked to do a study of shelters for abused and battered women to determine...
You are asked to do a study of shelters for abused and battered women to determine the necessary capacity I your city to provide housing for most of these women. After recording data for a whole year, you find that the mean number of women in shelters each night is 250 , with a standard deviation of 75 . Fortunately, the distribution of the number of women in the shelters each night is normal, so you can answer the following...
MATHEMATICS 1. The measure of location which is the most likely to be influenced by extreme...
MATHEMATICS 1. The measure of location which is the most likely to be influenced by extreme values in the data set is the a. range b. median c. mode d. mean 2. If two events are independent, then a. they must be mutually exclusive b. the sum of their probabilities must be equal to one c. their intersection must be zero d. None of these alternatives is correct. any value between 0 to 1 3. Two events, A and B,...
1. The use of a production smoothing strategy creates inventory for products that experience a seasonal...
1. The use of a production smoothing strategy creates inventory for products that experience a seasonal fluctuation in demand.   True or False ? 2. Companies belonging to the same industry segment should have the same inventory turns.  True or False ? 3. Which of the following is a work-in-process inventory for C&A Bakery? A. Flour B. Cupcakes freshly out of the oven C. Ovens D. Cupcake mix prepared from scratch 4. C&A has on average $6000 in inventory and its daily...
Andretti Company has a single product called a Dak. The company normally produces and sells 88,000...
Andretti Company has a single product called a Dak. The company normally produces and sells 88,000 Daks each year at a selling price of $56 per unit. The company’s unit costs at this level of activity are given below: Direct materials $ 9.50 Direct labor 9.00 Variable manufacturing overhead 1.90 Fixed manufacturing overhead 6.00 ($528,000 total) Variable selling expenses 2.70 Fixed selling expenses 4.50 ($396,000 total) Total cost per unit $ 33.60 A number of questions relating to the production...
What tools could AA leaders have used to increase their awareness of internal and external issues?...
What tools could AA leaders have used to increase their awareness of internal and external issues? ???ALASKA AIRLINES: NAVIGATING CHANGE In the autumn of 2007, Alaska Airlines executives adjourned at the end of a long and stressful day in the midst of a multi-day strategic planning session. Most headed outside to relax, unwind and enjoy a bonfire on the shore of Semiahmoo Spit, outside the meeting venue in Blaine, a seaport town in northwest Washington state. Meanwhile, several members of...
Delta airlines case study Global strategy. Describe the current global strategy and provide evidence about how...
Delta airlines case study Global strategy. Describe the current global strategy and provide evidence about how the firms resources incompetencies support the given pressures regarding costs and local responsiveness. Describe entry modes have they usually used, and whether they are appropriate for the given strategy. Any key issues in their global strategy? casestudy: Atlanta, June 17, 2014. Sea of Delta employees and their families swarmed between food trucks, amusement park booths, and entertainment venues that were scattered throughout what would...