# Standard Deviation

10,243 results

**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 ...

**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?

**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 ...

**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

**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 ...

**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**

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?

**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 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 ...

**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**

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 ...

**statistics**

30 new babies were born yesterday in the hospital. If the average weight of a new born is 7.5 pounds with a standard deviation of 2.1 pounds, what is the probability of the average weight for these 30 newborns is between 7.2 and 7.6 pounds. Remember, all probabilities are ...

**math**

The mean score on a Math exam was 50% and the standard deviation was 10%. Assume the results were normally distributed. (a) What percent of students earned a score between 50% and 70%? (b) If 60 students took the exam, how many got a score between 50% and 70%?

**AP Stats**

The mean weight of pears grown in a certain orchard is 6 ounces with a standard deviation of .5 ounces. A random sample of 30 pears is selected. What is the approximate probability that the sample mean weight is less than 5.5 ounces?

**math**

If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, what percentage of light bulbs have a life less than 2500 hours?

**statistics**

If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, what percentage of light bulbs have a life less than 2500 hours?

**Statistics**

If light bulbs have lives that are normally distributed with a mean of 2500 hours and a standard deviation of 500 hours, what percentage of light bulbs have a life less than 2500 hours

**MATH 2**

It is found that the number of raisins in a box of a popular cereal is normally distributed, with a mean of 133 raisins per box and a standard deviation of 10 raisins. My cereal box has 147 raisins. What is the z-score for this box of cereal?

**MATH**

it is found that the number of raisins in a box of a popular cereal is normally distrubuted, with a mean of 133 raisins per box and a standard deviation of 10 raisins. my cereal box has 152 raisins, what is the z-score for this box of cereal?

**Statistics**

The heights of 18-year-old men are approximately normally distributed with mean 68 inches and standard deviation 3 inches. What is the probability that the average height of a sample of ten 18-year-old men will be less than 70 inches? Round your answer to four decimal places. ...

**statistics**

A cell phone service provider has selected a random sample of 20 of its customers in an effort to estimate the mean number of minutes used per day. The results of the sample included a sample mean of 34.5 minutes and a sample standard deviation equal to 11.5 minutes. Based on ...

**math**

if, instead of assuming that the mean body temperature is 98.20 degree Ferinheight, we assume that the mean is 98.60 F(as many people believe), wht is the chance of randomly selecting 106 people and getting a mean of 98.20 degree F or lower? (continue to assume that the ...

**Statistics**

A manufacturer of a low-tar cigarette claims that their cigarettes contain an average of 16.3 mg of tar with a standard deviation of 3.1 mg per cigarette. How many sample cigarettes must the manufacturer observe to be 99% confident that the width of the confidence interval is ...

**algebra homework check**

The monthly rents for the apartments in a Business 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???

**Management**

The bulbs manufactured by a company gave a mean life of 3000 hours with standard deviation of 400 hours. If a bulb is selected at random, what is the probability it will have a mean life less than 2000 hours? Question: 1) Calculate the probability. 2) In what situation does ...

**fnu**

The average age of doctors in a certain hospital is 50.0 years old. Suppose the distribution of ages is normal and has a standard deviation of 4.0 years. If 16 doctors are chosen at random for a committee, find the probability that the average age of those doctors is less than...

**statistics**

The average age of doctors in certain hospital is 43 years old. Suppose distribution of ages is normal and the standard deviation is 8.0 years. If 25 doctors is chosen at random for a committee, find the probability the average age for those doctors is less than 43.8 years. ...

**statistics**

we want to if men and women perform differently on statistics tests. The average of 15 men's scores was 76. The average of 10 women's scores was 83. The standard deviation in both cases is 10. Test at 5% significance level. what is the null and alternate hypothese? is it a one...

**statistics**

A charity believes that when it puts out an appeal for charitable donations the donations it receives will normally distributed with a mean of $50 and standard deviation of $6, and it is assumed that donations will be independent of each other. (i) Find the probability that a ...

**statistics**

calculate the correlation for data set A. Data Set A: xi = 65, 55, 50, 45, 35 yi= 44, 52, 68, 20, 36 I know how to find the mean, variance, standard deviation, and z-score. The part I am having trouble finding is the ZxiZyi. In the chart that I have to fill in it says Zxi in ...

**Stats....how do i do this??**

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? Im not sure how to do this...

**statistics**

Assume that women's heights are normally distributed with a mean=63.6 in. and standard deviation = 2.5 in. a) To be eligible for the US Marine Corps, a woman must have a height between 58 in. and 73 in. Find the percentage of women who satisfy that requirement. b)If the ...

**Algebra 2**

Times for an ambulance to respond to a medical emergency in a certain town are normally distributed with a mean of 450 seconds and a standard deviation of 50 seconds. Suppose there are 160 emergencies in that town. In about how many emergencies are the response times expected ...

**Statistics**

Second Problem A. determine the mean, median, and the standard deviation B. Determine the coefficient of skewness using Pearson's method C. Determine the coefficient of skewness using the software method Commison earned($000)last year by the sales representatives at the ...

**Math**

What is the difference between the height of the tallest man at 92.95" and the mean height of men 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 ...

**statistics**

Boxes of bran flakes are known to be normally distributed with a mean weight of 475g and a standard deviation of 10g.Calculate the probability of a box having a weight exceeding 485 grams. Calculate the probability that the mean weight of sixteen boxes will exceed 480g.

**statistics**

the weights of shells follow a normal distribution. a random sample of 12 hybrid shells a a mean weight of 1.7 pounds with standard deviation 0.24 pounds. Find a 95 % confidence interval level for the mean weight if the fall catch is within 0.1 pounds of the sample estimate

**statistics**

A study of the time spent shopping in a supermarket for a market basket of 20 specific items showed an approximately uniform distribution between 20 minutes and 40 minutes. What is the probability that the shopping rime will be a. Between 25 and 30 minutes? b. less than 35 ...

**statistics for health research**

the income of a group of 10,000 health system employees was found to be normally distributed with a mean=750 pm and standard deviation=50. show that of this group about 95% had income exceeding 668 and only 5% had income exceeding 832

**Statistic**

A random sample of size 20 drawn from a normal distribution has a sample mean of 8 and a sample standard deviation of 4. A) Compute the sample test statistic t under the null hypothesis H_0: Mue(mean)=7 B) State the alternate hypothesis if you believe that the population mean ...

**statistics**

The physical plant at the main campus of a large state university receives daily requests to replace florecent lightbulbs. The distribution of the number of daily requests is bell-shaped and has a mean of 37 and a standard deviation of 3. Using the empirical rule (as presented...

**stats**

Scores on a test are approximately normally distributed with a mean of 70 and a standard deviation of 9. The teacher wants to give A’s to the top 10% of students, B’s to the next 25%, and C’s to the next 42%. a.) what is the bottom cutoff for a C grade? b.) what is the ...

**Bio**

im stuck on these questions for my study guide Please help! i don't want links. thanks 1. Which of the follwoing would be an appropriate measure of the phenotypic variation of a trait in a population? a) the mean of the trait in the population b) the standard deviation of the ...

**statistics**

Assume the population distribution of FEV is normal with standard deviation 400 mLi. (a) find P(E) is n=15 and population mean is 2800 mLi (B) find P(E) is n=15 and the population mean is 2600mLi (C) How does P(E) depend on the population mean?

**math**

No idea how to do this. I looked in my book and there usually is a data set present to get the first, second and third quartile. The lifetimes of lightbulbs of a particular type are normally distributed with a mean of 392 hours and a standard deviation of 9 hours. Find the ...

**statistics**

Among coffee drinkers, men drink a mean of 2.8 cups per day with a standard deviation of 0.5 cups. Assume the number of drinking per day follows a normal distribution. What proportion drink 3 cups per day or more?

**statitics**

Certain data includes 36 body temperatures for which the sample mean is equal to 98.20 °F and standard deviation of 0.62 °F. Using this sample statistics, construct a 95% confidence interval of the mean body temperature. What does the sample suggest about the use of 98.6°F ...

**homework statistics**

Consider a random sample with sample mean x. If the sample size increased from n = 40 to n = 360, then the standard deviation of x will: a. remain the same b. increase by a factor of 9 (will be multiplied by 9) c. decrease by a factor of 9 (will be multiplied by 1/9) d. ...