Explore BrainMass

Standard Deviation

Standard deviation is a measure of absolute variation used to calculate the amount of divergence which exists from an expected value and is denoted by the Greek symbol for sigma. Out of all the measures of dispersion and spread, standard deviation is the most frequently utilized and it is advantageous in that it can easily detect for skewness (1).

The variables in this equation are:
σ = standard deviation (in this equation it is denoted by the letter s)
x = each value in the population
xbar = mean of sample
n = number of scores



Find confidence interval using standard normal distribution

Q1 You are a proprieter of NYC boutique. You want to know the average age of your customers. You take a random sample of 25 customers which yields an average age of 32 yrs with a standard deviation of 8. You have reason to belive the distibution of ages is normally distributed. Determine a 95% confidence interval for the age

Computing and analyzing the simple regression equation

Enterprise Industries produces Fresh, a brand of liquid laundry detergent. In order to study the relationship between price and demand for the large bottle of Fresh, the company has gathered data concerning demand for Fresh over the last 30 sales periods ( each sales period is four weeks). Here, for each sales period, y = dem

Computing mean, variance and standard deviation

1) Please calculate the standard deviation, mean, and variance for the dataset below (round to the nearest 2 decimal places where applicable). Men's 400 Meter Race Athlete Country Time LaShawn Merritt USA 43.75 Jeremy Wariner USA 44.74 David Neville USA 44.80 Chris Brown BAH 44.84 Leslie Djhone FRA 45.11 Ma

Cronbach's Alpha - Calculation and Interpretation using SPSS

Calculate Cronbach's alpha on the scale provided on pp. 710-711 of the Field text using the SAQ.sav file. Here is the scale provided on pp, 710-711 of the Andy Field text book: 1 Subscale 1 (Fear of statistics): items 1, 3, 4, 5, 12, 16, 20, 21 2 Subscale 2 (Peer evaluation): items 2, 9, 19, 22, 23 3 Subscale 3 (Fear of co

Project Management: PERT Network Diagram

The information presented in Table 1 represents the optimistic activity time (a), most probable activity time (m), and pessimistic activity time (b) in weeks for each activity associated with the project. See attached file for table 1. 1. What is the expected activity time (t) in weeks for each activity? Enter this infor

Management and Statistics

Please provide a short review of concepts and examples of: sample, measures of central tendency (mean value), and measure of variation (range, standard deviation σ) related to business management. In addition, could you show how these various elements are determined mathematically.

Calculating Standard Deviations

5.The credit manager of a discount sports equipment store believes that the average age of his charge account customers is 30 years. His deputy contends that the average age is less than 30 years. A random sample of 100 charge account customers showed the mean age as 27 years with a standard deviation of 10 years. Do these data

Cusum Chart

The data in the following table are individual temperature readings from a chemical process in oC, taken every two minutes (read in sequence top to bottom and left to right). The target value for the mean is 950 oC. (a) Estimate the process standard deviation. (b) Set up and apply a tabular cusum chart for this process, using

Observed significance level

For each of the below questions (1, 3, 5), determine the observed significance level. How would I do this? 1. The data below represents a random sample of weights (in grams) from a batch of a particular product. The nominal value is 87.5 grams. Prove that this sample is consistent with the nominal value, to a 90% confidence

Sample Statistics Problems

1. A survey of 400 people who took vacations revealed that 242 of them flew to their destination. Give a 95% confidence interval for the percentage of all people who fly when they take a trip. Does it appear statistically correct to conclude that more than 50% of all people who take vacations will fly to their destination? Why

Determining Statistics or Parameters

The personnel director of a corporation will study the overtime work during the previous year for the 2,575 clerical workers. A sample of 100 of these workers will be chosen at random from the files. The average and the standard deviation of the overtime hours will be calculated and the number of these employees who worked more

4 Books, Calculate the Mean and Standard Deviation.

Please show ALL steps. On your shelf, you have four books that you are planning to read in the near future. Two are fictional works, containing 212 and 379 pages, respectively, and the other two are non -fiction, with 350 and 575 pages respectively. (a) Compute the population mean  and standard deviation  of the (paren

Gallup Organization released results of a poll comparing lifestyles

On January 7, 2000, the Gallup Organization released the results of a poll comparing lifestyles of today with those yesteryears. Then poll results were based in telephone interviews with a randomly selected national sample of 1,031 adults, 18 years and older, conducted December 20-21, 1999. One question asked if the respondent h

Six Sigma Analysis

1. A company makes a part with a diameter of 1 inch with a tolerance of plus or minus .005 of an inch. The process has a mean of 0.997 and a standard deviation of 0.001 inch. Is the process capable? Why or why not? 2. A company owns a lease granting it the right to explore for oil on a property. The company may sell the l

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

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.

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 between juvenile delinquency and poor verbal abilitiies

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

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

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.

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

Standard Deviation

Suppose that the income of gas stations in the state average 29,000 with a standard deviation of 5,100. If there are 189 gas stations with an income between 26,000 and 31,000, how many gas stations (total) are there in the state?


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