Share
Explore BrainMass

Standard Deviation

Standard deviation of the lengths of pipes in a sample

Find the 95% confidence interval for the standard deviation of the lengths of pipes if a sample of 26 pipes has a standard deviation of 14.6 inches. Show me step by step how to solve this problem and what identifies the equation to use.

Population standard deviation problem

Population standard deviation The ages (in years) of the 6 employees at a particular computer store are 32, 35, 31, 27, 32, 35 Assuming that these ages constitute an entire population, find the standard deviation of the population. Round your answer to at least two decimal places. See the attached problem.

Population of Heights of Male College Students

Assume that the population of heights of male college students is approximately normally distributed with mean m of 69.09 inches and standard deviation s of 4.71 inches. A random sample of 92 heights is obtained. Show all work. (A) Find p(x>68.5) (B) Find the mean and standard error of the distribution (C) Find p(x

Mean, Variance & Standard Deviation

The following data lists the average monthly snowfall for January in 15 cities around the US: 42 45 8 18 45 15 31 46 3 33 2 6 32 47 36 Find the mean, variance, and standard deviation.

Statistical Process Control for Quality Service Company

Twenty-five samples of size 6 resulted in x = 8.0 and R = 2.0 for the Quality Service Company's average time to complete an order. Compute control limits for x- and R-charts and estimate the standard deviation of the process.

Weight of 2009 Honda Civic XL

See attached file. The Excel file contains a single question (w/correct answer provided). The question was posed to a group of 21 respondents whose responses are shown. Referencing the 21 responses, compute the unknown values requested.

Compare social interactions of the two groups

It is well known that children with developmental delays (i.e., mild mental retardation) are slower, cognitively, than normally developing children. A study compared the social interactions of the two groups of children in a controlled playground environment. One variable of interest was the number of intervals of "no play" by e

Relationship-Juvenile delinquency and poor verbal abilities

Numerous studies have been dedicated to investigate the relationship between juvenile delinquency and poor verbal abilitiies. Assume that scores of Verbal Intelligence Quotient (IQ) test have a population mean ... a. What shape would you expect the sampling distribution of x bar for n=84 juveniles to have? Does your answer dep

Finding the Z Scores for Each X Value

For a population with of mean of = 100 and a standard deviation of =10. A. Find the z-score for each of the following x values: X = 105 X = 120 X = 130 X = 90 X = 85 x= 60 B. Find the scores (X value) that corresponds to each of the following z-scores: z = -1.00 z = -0.50 z= 2.00 z = 0.70 z = 1.50 z= - 1

Which supplier of rivets should the manufacturer go with?

A manufacturer of a certain type of large machine wishes to buy rivets from one of two suppliers. It is important that the breaking strength of each rivet exceed 10,000 PSI. (Below 10,000 PSI results a defective rivet). Two suppliers (A & B) offer this type of rivet. Both have rivets whose breaking strength are normally dist

Pediatric lung function vs level of cigarette smoking in home

One suggested environmental determinant of pediatric lung function is the level of cigarette smoking in the home. A researcher wants to do a pilot study with two groups: Group 1 will consist of children up to 5 years of age with a mean FEV = 2.1 with standard deviation = 0.7. Both of the parents of these children will smoke.

Determining Sample Size of Two Groups

Mary is conducting a study and wants to determine sample size of two groups. One group has a mean of 3.5 with standard deviation of .8 the other group has a mean of 2.1 with a standard deviation of .5 How many N are needed in each group to have a 95% chance of detecting a significant difference using a two-sided alpha at

Customer delivery by truck: Process Capability Ratio and Six Sigma

A customer wants delivery to be ensured between 10 am and 2 pm. Your truck leaves the factory at 4 am and the time taken to reach the customer is normally distributed with an average of 8 hrs and a standard deviation of 1 hr. What is the process capability ratio of the process? If you want to improve the ability of the de

Computing Optimal Ordering Quantity Safety Stock

You are buying an important electronic component from a supplier in China. The component costs $360 and you incur a fixed shipment charge of $5000 whenever you order. You use a 20% interest rate to compute holding costs. The daily demand for the product is normally distributed with mean 5 pieces and standard deviation 2 pieces.

Population standard deviation for 5 newborn baby weights

Population standard deviation: In a particular hospital, 5 newborn babies were delivered yesterday. Here are their weights (in ounces): 130;130;99;110;126 Assuming that these weights constitute an entire population, find the standard deviation of the population. Round your answer to at least two decimal places. (If nec

Annual snowfall in a city, amount of money a student spends for books

1. Suppose the annual snowfall in a city is normally distributed with a mean of 75 inches and a standard deviation of 20 inches. Find the probability that in a given year, snowfall in the city would be between 50 and 100 inches (that is, within §25 of 75). 2. Let X denote the amount of money a student spends on books in

Copy Machine Hours and Annual Textbook Sales

#1 The time, in hours, that a copying machine may work without breaking down is a normally distributed random variable with the mean 549 and the standard deviation 68. Find the probability that the machine will work for at least 500 hours without breaking down - explain your answer (study guide problem 59). #2. Total annua

Upper/lower control limits for Quality Textiles International

Quality Textiles International is an organization that weaves fabric and then prepares the required sheet lengths as desired by customers. They have received recent complaints that the fabric weight, measured in oz per square inch, is not meeting customer requirements, which are very close to the control limits. Quality Textiles

Statistics demand patterns for vinyl washers: relative variation

A plumbing supplier's mean monthly demand for vinyl washers is 24,212 with a standard deviation of 6,053. The mean monthly demand for steam boilers is 6.8 with a standard deviation of 1.7. Compare the dispersion of these distributions. Which demand pattern has more relative variation?

Chebychev's Theorem and Empirical Rule

If we are dealing with non-normal data we use Chebychev's Theorem. While not as precise, it does provide some level of utility. If we use Chebychev, how many standard deviations do we have to go out from the mean, in order to approach roughly the same level of precision provided by plus or minus two SDs under the Empirical Rul

Mean, standard deviation for number of left-handed people

Ten percent of American adults are left-handed. Suppose we have a sample of 25 people. Assume that each person in the sample is either left or right-handed. a) Find the mean and standard deviation for the number of left-handed people in the sample. Mean= 2.5 standard deviation = 1.5 b) Would it be unusual to sur

Chebysef's Inequality Problem

2. (Moments and Chebyshef's inequality, 8 points) A random variable X has E[X] = 10 and Var[X] = 100. (a) Find the smallest upper bound for P(X (greater than or equal to) 40) (b) Can X be a binomial random variable? (c) Can X be a Poisson random variable? (d) Can X be Exponential?

Calculation of Sample Standard Deviation

Employees from five computer companies were surveyed to find their monthly income in hundreds of dollars. The data is shown below. Compute the sample standard deviation in hundreds of dollars. 17.4, 24.6, 36.2, 48.1, 48.7.

Dispersion of Two Distributions for Vinyl Washers and Boilers

A plumbing supplier's mean monthly demand for vinyl washers is 24,212 with a standard deviation of 6,053. The mean monthly demand for steam boilers is 6.8 with a standard deviation of 1.7. Compare the dispersion of these distributions. Which demand pattern has more relative variation? Explain.

Statistics

A set of final examination grades in an introductory quantitative analysis course is normally distributed, with a mean of 73 and a standard deviation of 8. a) What is the probability of getting a grade below 91 on this exam? b) What is the probability that a student scored between 65 and 89? c) The probability is

Statistics - Standard Deviation.

According to the U.S. Bureau of census current Construction TReport, the average price of a new mobile home in the western part of the United States during 1993 was $40,500. Assume the standard deviation was $8,500/ Should a mobile home selling for $75,000 be considered and outlier? Explain why or why not.