Standard Deviation Word Problems

If the life, in years, of a washing machine is normally distributed with a mean of 20 years and a standard deviation of 1.5 years, what should be the guarantee period if the company wants less than 1% of the machines to fail while under warranty?
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In a class of 25 students, the grades were normally distributed with a mean of 78 and a standard deviation of 5. Sketch the normal curve for the distribution. What percentage of the students scored above an 88? How many students scored above an 88?
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A manufacturer of automobile batteries claims that the average length of life for its grade "A" battery is 60 months. However the guarantee on this brand is just for 36 months. Suppose the standard deviation of the life length is known to be 10 months, and frequency distribution of the lifelength is known to be bell mound shape.
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A whole sale distributor has found that the amount of a customer`s order is a normal random variable with a mean of $200 and a standard deviation of $50. What is the probability that the total amount in a random sample of 20 orders is greater than $4500?
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mean height 65.5 inches and standard deviation 3.2 with normal distribution.
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At work Mr. Bussmann must wear a dress shirt, long pants, and shoes. He has four dress shirts(red, blue, orange, purple), three pairs of pants (green, yellow, tan) and two pair of shoes (white, black) Find out how many different outfit he has for work.
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For a normally distributed population, approximately 68 percent of the population lies within 1 standard deciation of teh mean and approximately 95 percent of the population lies within 2 standard deciations of the mean. In a certain environmental study, the weights of 10,000 fish are normally distributed with a mean of 12.5 ounces and a standard deciation of 4.2 ounces. Approximately what percent of the 10,000 fish have weights between 16.7 and 20.9 ounces?
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Assume that the length of time, x, between charges of a pocket calculator is normally distributed with a mean of 100 hours and a standard deviation of 15 hours. Find the probability that the calculator will last between 80 and 120 hours between charges
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A college only accepts top 10% of students. The average score is 1148.2 and the standard deviation is 121.6. What is the lowest score you can make and still get acepted?
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The amount of time required to assemble a component on a factory assembly line is normally distributed with a mean of 3.1 minutes nd a standard deviation of 0.6 minutes. Find the percentage of employees taht will take between 2.0 minutes and 2.5 minutes to assemble the component.
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The life expectansy in the United States is 75 with a standard deviation of 7 years. A random sample of 49 individuals is selected. What is the probability that the sample mean will be between 73 and 74 years
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a box contains 2 blue pins and 3 red pins, the color of a pin that is randomly chosen is recorded and the pin is returned to the box, given that this process is repeated 4 tomes and X is the number of times a blue pin is chosen, find the mean value and the standard deviation of X
Solve the problem.The scores on a certain test are normally distributed with a mean score of 48 and a standard deviation of 3. What is the probability that a sample of 90 students will have a mean score of at least 48.3162?

In a normal distribution, if the mean is 80 and the standard deviation is 10, what percentile corresponds to 1 standard deviation below the mean
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mean of 80 and a standard deviation of 14.0 compute the probability of a value between 75 and 90
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Suppose the standard deviation is 12.4. What is the variance?
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X mean and S deviation of asset 100 observation were worked out as 40 and 5 respectively by a computer who by mistake took the value 50 in place of 40 for one observation recalculate the correct mean and variance
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THE DISTRIBUTION OFSCORES ON A HISTORY TEXT IS CLOSE TO NORMAL. THE SCORES ARE ADJUSTED SO THAT THE MEAN SCORE IS 75 AND THE STANDARD DEVIATION IS 5. HOW HIGH MUST A STUDENT SCORE TO FALL IN THE TOP 25%.
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Suppose the standard deviation is 12.4 What is the variance?
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A 420 pound man breaks a chair at a restaurant due to his weight. The manufacturer of the chair states that the chair can support a 450 pound man with a standard deviation of 8. The restaurant argues that the average man weighs 185 pounds with a standard deviation of 31 pounds. The man sues for $1 million dollars for pain and suffering but only suffered minor bruises. Who has the stronger case, the man or the restaurant?
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Find the standard deviation for this data set, correct to the nearest tenth. 45 39 26 52 34 30
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the neck size of men is normally distributed, with a mean of 15.5 inches for a shirt with a 0.5 inch standard deviation, and a new line of 1,000 shirts will be introduced. How many shirts would have a neck size of 14?
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The mean amount of time that a manager spends in annual performance review with an employee is 27.2 minutes, with a standard deviation of 4.9 minutes. What percentage of the annual performance reviews in the department take between 22.3 and 32.1 minutes? Between 17.4 and 37 minutes? Between 12.5 and 41.9 minutes? Explain answer.
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At a fair, 37 pumpkins were entered for judging under the normal pumpkin division. If the masses are normally distributed and the average weight is 12.4 kg, with a standard deviation for 2.31 kg. What is the probability that a pumpkin has a mass between 13.5kg and 15kg?
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A potato chip company packages its potato chips into 12.0 ounce bags. You find it hard to believe that the bag contains enough potato chips to weigh 12.0 ounces and would like to make an official complaint. Before doing so, you decide to run an experiment so that you can have some confidence that the company’s claim is incorrect. Over the next several months you buy 30 bags of potato chips and weigh the contents of each one. You discover that the mean weight is 11.9 ounces with a standard deviation of 0.4 ounces. You decide that you will only complain if you can be 95% sure that the bags do not contain at least 12.0 ounces of potato chips. You decide to construct a hypothesis test.
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A student measures the length of a room to be 4.64 meters. If the actual length of the room is 5.80 meters, what is the student`s % deviation?
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According to the sleep foundation, the average night`s sleep is 6.8 hours (Fortune, March 20, 2006). Assume the standard deviation is .6 and that the probability distribution is normal. a. What is the probability that a randomly selected person sleeps more than 8 hours? b. What is the probability that a randomly selected person sleeps 6 hours or less? c. Doctors suggest getting between 7 and 9 hours of sleep each night. What percentage of the populations gets this much sleep?
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For a normally distributed population, approximately 68 percent of the population lies within 1 standard deviation of the mean and approximately 95 percent of the population lie within 2 standard deviations of the mean. In a certain environmental study, the weights of 10,000 fish are normally distributed with a mean of 12.5 ounces and a standard deviation of 4.2 ounces. Approximately what percent of the 10,000 fish have weights between 16.7 and 20.9 ounces?
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The mean mileage for a certain Minivan is 19.5 mpg with a standard deviation of 1.8 mpg a. Assuming we know nothing about the shape of the data set, at least what percentage of time will the recorded mileage will be between 16.8 and 22.2 mpg? b. Assuming we can verify that the data set is approximately normally distributed, what percentage of time will the recorded mileage be greater 15.9 mpg? c. Assuming we can verify that the data set is approximately normally distributed, 68% of the mileages will be within what range?
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The average salary for firstyear teachers is $27,989. If the distribution is approximately normal with a standard deviation of $3250, what is the probability that a randomly selected firstyear teacher makes these salaries? a. between $20,000 and $30,000 per year; b. less than $20,000 per year.
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Z Score IQ between 90 and 100 Problems and Answers

Standard deviation of a group of 40 students` test scores was calculated as 6.5 points on a 100 point test and the mean of thier distribution of scores was 75.5 points. vind z value of each students` scores
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A tire company tested another model of tire and found the tires to be normally distributed with respect to wear. The average (mean) tire wore out at 46,000 miles, and the standard deviation was 24,000. IF 2000 tires were tested, about how many are likely to wear out before 45,000 miles?
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the average blood pressure of a group of men is 125 mm and the sd is 15 mm. a histogram of the blood pressures is roughly bell shaed. About 25 % of the men have blood pressure less than __?
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Jeannie is an experienced business traveler, often traveling back and forth from San Francisco to the East Coast several times per month. To catch her flights from San Francisco she leaves her office one hour before her flight leaves. Her travel time from her office to the departing gate at the San Francisco airport, including the time to park and go through security screening, is normally distributed with a mean of 46 minutes and a standard deviation of 5 minutes. What is the probability that Jeannie will miss her flight because her total time for catching her plane exceeds one hour? Round your final answer to 4 decimal places.
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Suppose the standard deviation is 12.4.
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1n 1995, the life expectancy of males in a certain country was 71.3 years. In 2001 it was 75.1 years. Let E represent the life expectancy in year and let t represent the number of years since 1995. E(t)=_t+_ and E(10)=__ I don`t know the right data, if it is right in front of me.
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a population has a mean of 300 and a standard deviation of 18. a sample of 144 observations will be taken. the probability that the sample mean will be between 297 to 303 is
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THE PROBAABILITY OF WINNING A VERTAIN LOTTERY IS 1/51, 949. FOR PEOPLE WHO PLAY 560 TIMES, FIND THE STANDARD DEVIATION FOR THE RANDOM VARIABLE x, THE NUMBER OF WINS.
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Find the IQ score separating the top 85% from the others. Assume adults that have IQ scores that are normally distributed with a mean of 100 and a standard deviation of 15.
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In Prof. Smith`s management course the correlation between the students` total score before the final examination and their final examination scores is r=.06. The preexam totals for all students in the class have mean 280 and standard deviation of 30. The final exams scores have mean of 75 and standard deviation of 8. Prof Smith lost Suee`s final exam but knows that her total before the esam was 300. He decides to predict her final exam score from her preexam total.
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Test for high school students with a 3.50 to 4.00 grade point average were normally distributed, with a mean of 38.8 and a standard diviation of 1.9. A student with a 3.5 to 4.00 grade point average who took the standarized tes is randomly selected. The probability of a student scoring less than 36 is?
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A reading program is administered to the bottom 5% of the students. If the average score of the students is 122.6, find the cutoff score that will make a student eligible to the program. The standard deviation is 18 and assume that the variable is normally distributed.
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A pediatrician`s records show that height of a random sample 25 girls at age 12 months to be 29.530 inches with a standard deviation of 1.0953 inches. Construct a 95 percent confidence interval for population variance.
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With a height of 69 inches, Alexander was the shortest president of a particular club in the past century. The club presidents of the past century have a mean height of 75.4 inches and a standard deviation of 2.7. a. What is the difference between Alexander`s height and the mean? b. How many standard deviations is that [the difference found in part a]?
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In France, years of life expectancy are normally distributed with a mean of 81 years and a standard deviation fo seven years. For the French population: a) What is the probability of living 92 years or more? b) What is the probability of living between 78 and 88 years?
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A normal distribution has a mean of 80 and a standard deviation of 14. Determine the value above which 80% of values will occur?
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standard devition for number of cars in different nations (per 100 population): United States 50; Canada: 45; France 47; Germeny 21; Japan 40; Mexico 10.
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A dailly record was kept of the number of animals each worker stuffed at a toy factory. Each stuffed animal was 40 cents per completely stuffed animal. At the end of the summer, each of the two workers had the same mean number but Bob had a standard deviation of 18 while mike had a standard deviation of 8. which earned more?

The amount of soda a dispensing machine pours into a 12 ounce can of soda follows a normal distribution with a mean of 12.24 ounces and a standard deviation of 0.16 ounces. The cans only hold 12.40 ounces of soda. Every can that has more than 12.40 ounces of soda poured into it causes a spill and the can needs to go through a special cleaning process before it can be sold. What is the probability a randomly selected can will need to go through this process?

IN A CLASS,THE MEAN SCORE IS 60.STANDARD DEVIATION =4.2,JOHN`S SCORE=2 STANDARD DEVIATION AWAY FROM THE MEAN.WHAT IS JOHN`S SCORE?

a normal population has a mean of 75 and a standard deviation of 5. Between 74 and 76 less than 74 between 76 and 77 greater than 77

2500 employess avg 15.5 years standard devitation 6.1 years how many with over 18 yrs

Assume that the length of time, x, between charges of a pocket calculator is normally distributed with a mean of 100 hours and a standard deviation of 15 hours. Find the probability that the calculator will last between 80 and 120 hours between charges.

For a student to graduate, a high school requires that each student demonstrate competience in mathemantics by scoring 70 or above on a mathematics achievement test. The scores of those students taking th test are normally distributed with a mean of 74 and a standard deviation of 4.8. Find the score seperating the top 10% from the others.

Suppose the standard deviation is 12.4. What is the variance

1. In Prof. Smith’s math course the correlation between the students’ total scores prior to the final examination and their final examination scores is r=0.7. The preexam totals for all students in the course have mean 280 and standard deviation 30. The final exam scores have mean 75 and standard deviation 8. Prof. Smith has lost Julie’s final exam but knows that her total before the exam was 300. He decides to predict her finalexam score from her preexam total. (a). Based on the question above, what is the response variable (y) in the regression model? What is the explanatory variable (x)? Variable response (y) is Explanatory variable (x) is


If the standard deviation is 16.9% and the average is 73.2%, what grade would the student receive if she got an 80%?

1. The mean amount of time required by an appliance repairman to fix a washing machine is 48 minutes with a standard deviation of 6 minutes. At least what percent of the machines should take between 30 and 66 minutes to repair?

A normal distribution has a mean of 20 and a standard deviation of 5. Ninetyfive percent of the scores fall between

Suppose the average score on the GMAT is 500 and the standard deviation is 100 points. You would expcet approximately 95% of all GMAT scores to be between?