# Standard Deviation

10,416 results, page 32

### Stats

Consumer Reports rated airlines and found that 80% of flights involved in the study arrived on time (that is, within 15 minutes of scheduled arrival time). Assuming that the on-time rate is representive of the entire commercial airline industry, consider a random sample of 200...

### statistics

Suppose that, in fact, the blood cholesterol level of all men aged 20 to 34 follows the normal distribution with mean of u = 188 milligrams per deciliter (mg/dl) and standard deviation = 41 mg/dl. 1. Choose an SRS of 100 men from this population. What is the sampling ...

### Math

For the most recent year available, the mean annual cost to attend a private university in the United States was $20,082. Assume the distribution of annual costs follows the normal probability distribution and the standard deviation is $4,500. Ninety-five percent of all ...

### statistics

AAA reports that the average age of a car on U.S. roads in recent years has risen to 7.5 years. Suppose that the distribution of the age of automobiles assumes a mound shaped distribution. If 99.7% of the ages are between 1 year and 14 years, what is the value of the standard ...

### Stats

Suppose a Normal model describes the fuel efficiency of cars currently registered in your state. The mean is 27 mpg, with a standard deviation of 4 mpg. Describe the mileage of the most efficient 3% of all cars. a. greater than 24.9 mpg b. greater than 19.5 mpg c. greater than...

### Precalculus

Suppose that the mean score of 250,000 students on the mathematics part of the SAT is 468 and the standard deviation is 104. Suppose that you make 650 on the SAT mathematics part. a. How many standard deviations is your score above the mean? How do you do this? b. What ...

### Precalculus

Suppose that the mean score of 250,000 students on the mathematics part of the SAT is 468 and the standard deviation is 104. Suppose that you make 650 on the SAT mathematics part. a. How many standard deviations is your score above the mean? How do you do this? b. What ...

### Normal Probability Distribution

A professor at a local college noted that the grades of his students were normally distributed with an average percentage of 74 and a population standard deviation of 10. He found that 6.3% of his students received A's while 2.5% of his students failed the course and received ...

### Statistics

A study was conducted in order to estimate u, the mean number of weekly hours that U.S. adults use computers at home. Suppose a random sample of 81 U.S. adults give a mean weekly computer usage time of 8.5 hours and that from prior studies , the population standard deviation ...

### stats

An athletic director found that 31% of the football players have an A average in school. If 2% of the students at the school play football, what is the probability that a student chosen at random will be a football player with an A average? suppose a normal distribution has a ...

### math

A government survey conducted to estimate the mean of houses in a metropolitan area is designed to have a margin of error of 10,000. Pilot studies suggest that the population standard deviation is 70,000. Estimate the minimum sample size needed to estimate the population mean ...

### Finance

we have two stocks Stock A and Stock B, Both stocks have the same expected rate of return 11%, but have different Standard Deviation 12%, and 20% respectively. based on the information above can we conclude that any rational risk-averse investor will add stock A to a well ...

### stats

scores on the SAT critical reading test in 2013 follow a normal distribution with a mean score of 496 and a standard deviation of 115. what proportion of scores are higher thzn 530? what proportin of scores are between 400 and 500? the highest 10% of scored are higher than a ...

### math,help

how would i do about this problem can someone explain it to me or show me because i keep getting weird answers with an e at the end. It makes no sence. This question is: The length of human pregnancies from conception to birth varies according to a distrubition that is ...

### stats word problem Please help!

A. random sample of 50 four year olds attending daycare centers provided a yearly tuition average of 3987$ and the population standard deviation of $630. Find the 90% confidence interval of the true mean. and B. If a daycare center were starting up and wanted to keep tuition ...

### stats word problem Please help!

A. random sample of 50 four year olds attending daycare centers provided a yearly tuition average of 3987$ and the population standard deviation of $630. Find the 90% confidence interval of the true mean. and B. If a daycare center were starting up and wanted to keep tuition ...

### statistics

List below are the duration (in hours) of a simple random sample of all flights of a space shuttle program. Find the range, variance, and standard deviation for the sample data. Is the lowest duration time unusual? Why or hwy not? 73 95 238 199 166 268 198 374 260 235 382 339 ...

### statistics

A used car dealership has found that the length of time before a major repair is required on the cars it sells is normally distributed with a mean of 10 months and a standard deviation of 3 months. If the dealer wants only 5 percent of the cars to fail before the end of the ...

### tempe

An April 15, 2002 report in Time Magazine stated that the average age for women to marry in the United States is now 24.5 years of age. If the standard deviation is assumed to be 4.1 years, find the probability that a random sample of 32 U.S. women would show a mean age at ...

### Statistics

An April 15, 2002 report in Time Magazine stated that the average age for women to marry in the United States is now 24.5 years of age. If the standard deviation is assumed to be 4.1 years, find the probability that a random sample of 32 U.S. women would show a mean age at ...

### science (chem& statistics)

For a wine titration my results obtained were... 0.6402%, 0.5814%,& 0.6006% the I calculated was 0.04936 according to my text sometimes the # is expressed in ppt or 100% first which would be correct if asked to submit a RSD for the results of a lab like this and 2nd what would...

### Stats

The height of adult women in the U.S. is normally distributed, with a mean height of 64 inches and a standard deviation of 3 inches. With this in mind, answer the following: a) The shortest 10% of women are shorter than what height? b) The middle 75% of all women are between ...

### stats

The height of adult women in the U.S. is normally distributed, with a mean height of 64 inches and a standard deviation of 3 inches. With this in mind, answer the following: a) The shortest 10% of women are shorter than what height? b) The middle 75% of all women are between ...

### Statistics

SAT I scores around the nation tend to have a mean scale score around 500, a standard deviation of about 100 points, and are approximately normally distributed. What SAT I score within the population would have a percentile rank of approximately 16?

### statistics

SAT I scores around the nation tend to have a mean scale score around 500, a standard deviation of about 100 points, and are approximately normally distributed. What SAT I score within the population would have a percentile rank of approximately 99?

### Elementary Statistics

There are 100 questions from an SAT test, and they are all multiple choice with possible answers of a,b,c,d,e. For each question, only one answer is correct, find the standard deviation for the numbers of correct answers for those who make random guesses for all 100 questions.

### Math

In a study of 800 men,diastolic blood pressure was found to be approximately normally distributed, with a mean of 84 millimeters (mm) of mercury and standard deviation of 10 millimeters. Use the 68-95-99.7% rule to determine what percentage of the test group had a diastolic ...

### Statistics

Suppose that grade point averages of undergraduate students at one university have a bell-shaped distribution with a mean of 2.62 and a standard deviation of 0.43. Using the empirical rule, what percentage of the students have grade point averages that are at least 3.48? ...

### Statistics

I need help on this one too. Any one willing to get me started? THANKS! Potassium is a mineral that helps the kidneys function normally. It also plays a key role in cardiac, skeletal, and smooth muscle contraction, making it an important nutrient for normal heart, digestive, ...

### math stats

These data are a sample of the daily production rate of fiberglass boats from Hydrosport, Ltd., a Miami manufacturer 17 21 18 27 17 21 20 22 18 23 The company production manager feels that a standard deviation of more than three boats a day indicates unacceptable production-...

### statistics

In a time-use study, 20 randomly selected managers were found to spend a mean of 2.40 hours each day on paperwork. The standard deviation of the the 20 scores is 1.30. Also, the sample data appear to have a bell-shaped distribution. Construct the 95% confidence interval for ...

### statistics

In a time-use study, 20 randomly selected managers were found to spend a mean of 2.40 hours each day on paperwork. The standard deviation of the the 20 scores is 1.30. Also, the sample data appear to have a bell-shaped distribution. Construct the 95% confidence interval for ...

### Math(Assignment Due

Please help me, I have know idea how to do this and the assignment is due today! A manufacturer is producing metal rods, whose lengths are normally distributed with a mean of 75.0cm and a standard deviation of 0.25cm. If 3000 metal rods are produced how many will be between 74...

### probability and statistics

a population forms a normal distribution with a mean of u=80 and a standard deviation of o=15. for each of the following samples, compute the z-score for the sample mean and determine whether the sample mean is a typical, representative value or an extreme value for a sample ...

### statistics

A purchasing agent wants to estimate the mean daily usage of rye flour. She takes a sample for 50 straight days and find that the sample mean is 180 lbs with a sample standard deviation of 38.5 lbs. a)State the 90% confidence interval for the mean.b) State the margin of error

### statistics

The length of country and western songs is normally distributed and has a mean of 200 seconds and a standard deviation of 30 seconds. Find the probability that a random selection of 9 songs will have mean length of 186.30 seconds or less. Assume the distribution of the lengths...

### fnu

The length of country and western songs is normally distributed and has a mean of 200 seconds and a standard deviation of 30 seconds. Find the probability that a random selection of 9 songs will have mean length of 186.30 seconds or less. Assume the distribution of the lengths...

### Math Statistic

A student randomly guessed the answers to a five question true/false test (there is a 50% chance of guessing correctly on each question). Find. 1. the probability that the student answers more than 1 question correctly 2. the expected number of correct answers 3.the standard ...

### Texas Southern University

In a respresentative study,a sample of n = 100 adolescents with a history of group participation is given a standardized self-esteem questionnaire. For the general po;ulation of adolescents, scores on this questionnaire form a normal distribution with a mean of u = 40 and a ...

### Statistics

What are the grand mean, the UCL and the LCL of a control chart for the mean? Why do you suppose + (with underline) standard errors are used in control charts and not two standard errors or even one standard error?

### behavioral statistics

How could you use standard scores and the standard distribution to compare the reading scores of two students receiving special reading resource help and one student in a standard classroom who does not get special help?

### math

A government survey conducted to estimate the mean price of houses in a metropolitan area is designed to have a margin of error of $10,000. Pilot studies suggest that the population standard deviation is $70,000. Estimate the minimum sample size needed to estimate the ...

### math

A government survey conducted to estimate the mean price of houses in a metropolitan area is designed to have a margin of error of $10,000. Pilot studies suggest that the population standard deviation is $70,000. Estimate the minimum sample size needed to estimate the ...

### statistic

Suppose a random sample of 25 students is selected from a community college where the scores in the final exam (out of 125 points) are normally distributed, with mean equal to 112 and standard deviation equal to 12. Find the probability that the sample mean deviates from the ...

### Statistics

A survey among freshmen at a certain university revealed that the number of hours spent studying the week before final exams was normally distributed with mean 25 and standard deviation 15. A sample of 36 students was selected. What is the probability that the average time ...

### statistics

A machine is designed to fill jars with 16 ounces of coffee. A consumer suspects that the machine is not filling the jars completely. A sample of 8 jars has a mean of 15.6 ounces and a standard deviation of 0.3 ounce. Is there enough evidence to support the consumer's ...

### chemistry

A scientist measures the standard enthalpy change for the following reaction to be -53.4 kJ : Ca(OH)2(aq) + 2 HCl(aq) CaCl2(s) + 2 H2O(l) Based on this value and the standard enthalpies of formation for the other substances, the standard enthalpy of formation of H2O(l) is kJ/mol

### chemistry

A scientist measures the standard enthalpy change for the following reaction to be -53.4 kJ : Ca(OH)2(aq) + 2 HCl(aq) CaCl2(s) + 2 H2O(l) Based on this value and the standard enthalpies of formation for the other substances, the standard enthalpy of formation of H2O(l) is kJ/mol

### Statistics (urgent)

A beverage comopany uses a machine to automatically fill 1-liter bottles. Assume that the population of volumes is normally distributed. The company wants to estimate the mean volume of water to within 1 ML. Determine the minimum sample size required to construct a 95% ...

### Statistics

By measuring the amount of time it takes a component of a product to move from one workstation to the next, an engineer has estimated that the standard deviation is 6 seconds. (a) How many measurements should be made to be 90% certain that the maximum error of estimation will ...

### Math

Suppose a brewery has a filling machine that fills 12 ounce bottles of beer. It is known that the amount of beer poured by this filling machine follows a normal distribution with a mean of 12.41 ounces and a standard deviation of 0.04 ounce. Find the probability that a ...

### statistics

the breaking strength of a cable known to be normally distributed with a mean of 4000kg and a standard deviation of 25kg.The manufacture prefers that at least 95% of its products meet a strength requirement of 4050 kg.Is this requirement being met? If not, by changing the ...

### statistics

the breaking strength of a cable known to be normally distributed with a mean of 4000kg and a standard deviation of 25kg.The manufacture prefers that at least 95% of its products meet a strength requirement of 4050 kg.Is this requirement being met? If not, by changing the ...

### statistics

the breaking strength of a cable known to be normally distributed with a mean of 4000kg and a standard deviation of 25kg.The manufacture prefers that at least 95% of its products meet a strength requirement of 4050 kg.Is this requirement being met? If not, by changing the ...

### statistics

assume adults have an IQ score that are normally distrubted with a mean of 105 and standard deviation of 20 A) find the percentage of adults that have an IQ between 94 and 116 B) find the percentage of adults IQ exceeding 120 C)Determine the 1st, 2nd, and 3rd quartiles for ...

### Statistics

(TCO A) Consider the following age data, which is the result of selecting a random sample of 20 United Airlines pilots. 47 45 45 52 58 55 58 44 42 38 45 52 48 47 51 45 52 42 37 40 a. Compute the mean, median, mode, and standard deviation, Q1, Q3, Min, Max for the above sample ...

### Statistics

A quality control inspector wants to estimate the mean inside diameter of the washers produced by a certain machine. A preliminary sample indicates that the inside diameters have a standard deviation of 0.30 millimeters. What sample size does he need to estimate the mean to ...

### Math

I am doing estimating Standard deviation of grouped data. I have done all the sum freg 60/ midpoint 2580/ x bar is 43 for all/ and total with x bar is 10260. Can you explain how to get the variance and sq root from these. I know that you have to fregx(mid-xbar)square2 and ...

### statistic

Sam pays $740 for his house, and he wants to see if he pays too much. He asks people who live on the neighborhood with the similar house sizes, and 10 of the people give him their prices. It is found out that the mean and standard deviation of the 10 houses on the neighborhood...

### Math 1

In a study of 500 men, diastolic blood pressure was found to be approximately normally distributed, with a mean of 82 millimeters (mm) of mercury and standard deviation of 10 millimeters. Use the 68-95-99.7% rule to determine what percentage of the test group had a diastolic ...

### Statistics

37% of all doctors are family practitioners. If there are 300 doctors in one city, what is the standard deviation for the number of family practitioners? What is the expected value for the number of family practitioners?

### Statistics

A private medical clinic wants to estimate the true mean annual income of its patients. The clinic needs to be within $500 of the true mean. The clinic estimates that the true population standard deviation is around $2,300. If the confidence level is 95%, find the required ...

### math

You are the buyer for your university bookstore. One of the textbooks has a cost to you of $104 and you sell it to students for $208. In this case, however, you cannot salvage any value from copies that do not sell because a new edition is published every semester. Demand for ...

### Statistics Question

Consumer Reports rated airlines and found that 80% of flights involved in the study arrived on time (that is, within 15 minutes of scheduled arrival time). Assuming that the on-time rate is representive of the entire commercial airline industry, consider a random sample of 200...

### statistics

you are asked to estimate the average weight of an adult male passenger for a study to maximize the number of seats in a certain airplane. you collect random weights of 1000 men passengers from a population of 100,000. you find that the average man in the sample weighs 180 ...

### statistics

Just wondering if someone is able to give instructions as to how to go about this questions? As part of a large research project, a social psychologist develops a measure of global environmental attitudes (i.e., general attitudes towards the environment). Scores on this ...

### PsyDAG homework check

The monthly rents for the apartments in a building are listed below. $425, $550, $550, $550, $650, $650, $650, $650, $800, $900 Part A: Find the mean$637.50 median=$650 mode=$650 range=$475 and standard deviation of the rents????

### homework check plz

The monthly rents for the apartments in a building are listed below. $425, $550, $550, $550, $650, $650, $650, $650, $800, $900 Part A: Find the mean$637.50 median=$650 mode=$650 range=$475 and standard deviation of the rents???

### Statistics

Calculate the following: a) Determine the sample size necessary to estimate a population mean to within 1 with a 90% confidence given that the population standard deviation is 10. b) Suppose that the sample was calculated at 150. Estimate the population mean with 90% confidence.

### algebra

55% of the people in a town have brown eyes. you choose a random sample of 200 people to survey regarding their eye color. What is the mean and standard deviation of the proportion of people in your sample that have brown eyes?

### Statistics

9. Assume the weight, W, of a randomly selected adult has a normal distribution with a mean of 175 pounds and a standard deviation of 10 pounds.. Find the probability, P(W < 190), that a randomly selected adult weighs less than 190 pounds.

### statistics

a random sample of 20 prices for summer sleeping bags was taken with a sample mean of $83.75 and a sample standard deviation of $29.97 a. Find a 95% confidence interval for the mean price of all summer sleeping bags. b. what is m i.e., what is the margin of error?

### stats

a random sample of 20 prices for summer sleeping bags was taken with a sample mean $83.75 and a sample standard deviation of $29.97 a) find a 95% confidence interval for the mean price of all summer sleeping bags b)what is m i.e. what is the margin f error?

### business analytics

waiting times for 64 randomly selected walk-in customers and determined that their mean waiting time was 15 minutes. Assume that the population standard deviation is 4 minutes. The 90% confidence interval for the population mean of waiting times is

### statistics

A sample of 25 different payroll depts. found that the employees worked an average of 310.3 days a year with a standard deviation of 23.8 days. What is the 90% confidence interval for the average days worked by employees in all payroll departments?

### MAT 201

The number of vacation days taken by employees of a company is normally distributed with a mean of 14 days and a standard deviation of 3 days. For the next employee, what is the probability that the number of days of vacation taken is less than 10 days? More than 21 days?

### maths

the mean wages is 75/day and SD wages is 5/day for a group of 1000 person and same is 60 and 4.5 for group of 1500 person.what is mean and standard deviation in total?

### Statistics

Use a x squared-test to test the claim about the population variance or standard deviation at the given level of significance and using the given sample statistics. Claim: ơ2 ≤ 60; α = 0.025. Sample statistics: s2 = 72.7, n = 15

### statistics

population mean=42.6 standard deviation=12 n=16 M=34.4. Is this mean a reasonable outcome for a sample of n=16, or is this sample mean very different from what would usually be expected? I obtained a z -score of -2.73. Thus, that would make the sample mean a reasonless outcome...

### Prob. & Statistics

If one event, say Black, has P(.70) and another event, say Red, has P(.30). What is the probability in ten events of alternating choices, Red then Black, and being 100% correct, 90% correct. What should be the expected % correct and what is the standard deviation?

### Excel formula help

Formula to multiply the number in cell 4k times standard deviation of the numbers in cell z2 through z10 I don't understand cell z2 through z10 I have never had excel (4kxz2xz10) Please write this correctly

### statistics

mean = 60 wpm standard deviation= 15 wpm a.What is the probability that a randomly selected typist's net rate is at most 60 wpm? less than 60 wpm? b. What is the probability that a randomly selected is between 45 and 90 wpm?

### Math

A company makes batteries with an average life span of 300 hours with a standard deviation of 75 hours. Assuming the distribution is approximated by a normal curve fine the probability that the battery will last:(give 4 decimal places for each answer) a. Less than 250 hours b...

### Statistics

The fracture strength of a certain type of manufactured glass is normally distributed with a mean of 579 MPa with a standard deviation of 14 MPa. (a) What is the probability that a randomly chosen sample of glass will break at less than 579 MPa? (b) More than 590 MPa? (c) Less...

### statistics

The value of the z-score that is obtained for a hypothesis test is influenced by several factors. Some factors influence the size of the numerator of the z-score and other factors influence the size of the standard error in the denominator. For each of the following indicate ...

### math

i don't understand standard form math and i have to questions what is nine hundredths in standard form and sixteen and six tenths in standard form?

### statistics

Help!!!!!! A confidence interval estimate for the population mean is given to be (39,90, 48.11) If the standard deviation is 11.473 and the sample size is 52 determine the maximum error of the estimate. determine the confidence level used for the given confidence interval

### statistics

The number of vacation days taken by employees of a company is normally distributed with a mean of 14 days and a standard deviation of 3 days. For the next employee, what is the probability that the number of days of vacation taken is less than 10 days? More than 21 days?

### statistics

a rocket club makes its own rockets. The rockets go to a mean height of 1100 feet with a standard deviation of 60 feet. if the club fires 36 rockets, what is probability that the mean heights of the rockets will be greater than 1080p feet

### statistics

The number of vacation days taken by employees of a company is normally distributed with a mean of 14 days and a standard deviation of 3 days. For the next employee, what is the probability that the number of days of vacation taken is less than 10 days? More than 21 days?

### Statistics

Use a chi-squared test to test the claim about the population variance or standard deviation at the given level of significance and using the given sample statistics. Claim: ơ2 ≤ 60; α = 0.025. Sample statistics: s2 = 72.7, n = 15

### AP Stats (math)

A large metropolitan area found that the time it takes for people to commute to work has a mean of 20.5 minutes and a standard deviation of 15.4 minutes. What is the probability that a random sample of 40 people have a mean commute time greater than 25 minutes?

### Math

If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, approximately what percentage of light bulbs has a life of more than 3000 hours? A. About 84% B. About 68% C. About 32% D. About 16% Answer B

### Math ---HELP!!!!!

If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, approximately what percentage of light bulbs has a life of more than 3000 hours? A. About 84% B. About 68% C. About 32% D. About 16% Answer B

### math

A tractor manufacturing company machines axles to extremely small tolerances. The main power axles have a mean diameter of 3.0000 inches and a standard deviation of 0.0050 inch. What is the probability that a given axle will have a diameter between 2.9915 and 3.0004 inches? ...

### Statistics

A battery manufacturer is positive that its AA batteries last for 1,000 hours. However, you’re working for Consumer Reports and you don’t agree with what they say about their product. So, you buy 400 batteries and you test them out. Your findings are that the batteries ...

### Math

For a binomial distribution with n=20 trials and probability of success p=.05, we let r= number of successes out of 20 trials. Use the normal approximation to estimate P(6<=r<=12). How does this value compare with the corresponding probability obtained using the binomial...

### math- study question for final

You are given a sample of 106 body temperatures having a mean of 98.2 F and a standard deviation of 0.62 F. You are asked to test the hypothesis that the population mean body temperature is 98.6 F using a 0.05 significance level. What value should you use for the test ...

### statistics

What is the difference between the height of the tallest man at 92.95" and the mean height of me at 69.6" and a stanard deviation of 2.8? How many standard deviations is that? Convert tallest man to a z score Does tall mans height meet the criterion of being unusual by ...