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Dispersion and Spread of Data

Random Sampling and Error

6.1 Consider the following data to be a population of N=20 values ______________________________________________________________ 5 3 2 6 6 7 3 3 6 7 7 9 7 5 3 12 6 10 7 2 ___________________________

Confidence Interval and Random Sample

1. A confidence interval for a population mean has a margin of error of 10.7. What is the length of the confidence interval? 2. A random sample of size 17 is taken from a population. A normal probability plot of the sample data is found to be very close to linear. The population standard deviation is unknown. The appropriate m

Probability and Standard Deviation Questions

1. The time that the customers at the "self serve" check out stations at the Mejers store spend checking out follows a uniform distribution between 0 and 3 minutes. a. Determine the height and draw this uniform distribution. b. How long does the typical customer wait to check out? c. Determine the standard deviation of the

Probability & Standard Deviation

14. A file cabinet manufacturer estimates that 5% of its file cabinets will have drawers that close improperly. Assume a production run of 120 cabinets is completed. a. What is the mean and standard deviation of this distribution? b. What is the probability that 7 or more are defective? c. What is the probability that exactly

Studentized and Standardized Version

A variable has a mean of 144 and a standard deviation of 25. Five observations of this variable have a mean of 156 and a sample standard deviation of 16. Determine the observed value of the a. standardized version of x (x with dash over, see attachment) b. studentized version of x (x with a dash over, see attachment).

Homogeneity of Variance Test in SPSS

1. Using SPSS, check the following data for homogeneity of variance: Group 1 Group 2 Group 3 1 1 1 2 4 8 3 9 18 4 16 32 a) Using an alpha of .05, what can you conclude about homogeneity of variance from the output? Word process your response

Standard Deviation

The true length of boards cut at a mill with a listed length of 10 feet is normally distributed with a mean of 123 inches and a standard deviation of 1 inch. What proportion of the boards will be over 125 inches in length?

Calculation of mean and variance of a discrete random variable

1. Suppose that a variable x has the following distribution function: x p(x) 3 0.23 5 0.41 9 0.36 What is the population mean? 2. Suppose that a variable x has the following distribution function: x p(x) 1 0.18 6 0.16 9 0.15 24 0.51 What is F(9)? 3. Suppose that a variable x has th

Difference of the Standard Deviations of the Treatment Effect

RESEARCHERS at a university conducted experiments with poplar trees. Listed below are weights (kg) of poplar trees given no treatment and poplar trees treated with fertilizer and irrigation. Does there appear to be a difference between the two standard deviations? No treatment: 0.15 0.02 0.16 0.37 0.22 fertilizer and irrig

What do you think the market shares will be next month?

Over any given month, Dress-Rite loses 10% of its customers to Fashion, Inc., and 20% of its market to Luxury Living. But Fashion, Inc., loses 5% of its market to Dress-Rite and 10% of its market to Luxury Living each month; and Luxury Living loses 5% of its market to Fashion, Inc., and 5% of its market to Dress-Rite. At the p

Probability calculations based on normal probability

1. Suppose that the random variable x is normally distributed with mean = 1,000 and standard deviation = 100. Sketch and find each of the following probabilities: a. P(1,000<_x<_1,200) e. P(x<_700) b. P(x>1,257) f. P(812<_x<_913) c. P(x<1,035) g. P(x>891) d. P(85

Mean and Standard Deviations

Advertising expenses are significant component of the cost of goods sold. Listed below is a frequency distribution showing the advertising expenditures for 60 manufacturing companies located in the Southwest. Estimate the mean and the standard deviation of advertising expense. See attached file for chart.

Quartiles, deciles, and various percentiles.

The Thomas Supply Company, Inc. is a distributor of small electrical motors. As with any business, the length of time customers take to pay their invoices is important. Listed below, arranged from smallest to largest, is the time, in days, for a sample of The Thomas Supply Company, Inc. invoices. a. Determine the first and t

Normal Probability..

Ayrshire cows average 47 pounds of milk a day with a standard deviation of 6 pounds. For Jersey cows the mean daily production is 43 pounds, with a standard deviation of 5 pounds. Assume that normal models describe milk production for these breeds. One farmer has 20 jerseys, while a neighboring farmer has 10 Ayrshires. What'

Question on Basic Statistics

I need to research the definition of what is called the distribution of a data population. Also, I need to find the statistic that measures the width of dispersion ("looseness" or "tightness") of the population data about its mean.

Computing z values

A recent article in the Cincinnati Enquirer reported that the mean labor cost to repair a heat pump is $90 with a standard deviation of $22. Monte's Plumbing and Heating Service completed repairs on two heat pumps this morning. The labor cost for the first was $75 and it was $100 for the second. Compute z values for each and

Control Plan Problem

Problem #1 According to the control plan, 8 bolts will be measured every half hour and the machine will will be stopped if it is out of adjustment. Ninety-five percent of the bolts should be within 4+ or - .0004 inches. The last act of 8 showed the following measurements: 4.001 3.998 4.009 3.997 3.990 4.002 3.998

Mean & Standard Deviation of Time Required for Chemical Reaction

Laboratory data show that the time required to complete two chemical reactions in a production process varies. The first reaction has a mean time of 40 minutes and a standard deviation of 2 minutes; the second has a mean time of 25 minutes and a standard deviation of 1 minute. The two reactions are run in sequence during product

Statistics with Z scores and Bayesian Statistics

1. What is the term Bayesian statistics used to indicate? 2. What are the states of nature? 3. What is a variable? 4. What is a z score? 5. How does a z score differs from a t score? 6. What does the symbol sX represent? 7. What is the symbol for standard deviation? 8. What is one formula that we can use to calcula

Six months after a divorce, the former wife and his band each

Six months after a divorce, the former wife and husband each take a test that measures divorce adjustment. The wife's score is 63 and the husband's score is 59. Overall, the mean score for divorced women on this test is 60(SD=6); the mean score for divorced men is 55(SD=4). Which of the two has adjusted better to the divorce

Statistics: Arranging Data, Quartiles, Box plot, Mean Problems are attached.

16. Millionaires: The ages of the 36 millionaires sampled are arranged in increasing order in the following table. 31 38 39 39 42 42 45 47 48 48 48 52 52 53 54 55 57 59 60 61 64 64 66 66 67 68 68 69 71 71 74 75 77 79 79 79 a. Determine the quartiles for the data. b. Obtain and interpret the interquartile range.

Stocks Based on Covariance

You own a stock called Insurate, Inc. Your profit for the stock is a random variable (W) with mean 1,000 and variance 400. You would like to buy more stock and you are trying to decide between Insurate (Y) and Mutual Fund, Inc. (F). Both of these stocks have a mean of 1,000 and a variance of 400. Which stock should you choose gi

Gamma Distribution

Suppose that when a transistor of a certain type is subjected to an accelerated life test, the lifetime X (in weeks) has a gamma distribution with mean ... (see attachment)


1. Compute the mean, median, and mode for each of the following distributions. A B C D 3 2 1 2 3 2 3 3 4 2 3 4 6 5 3 4 7 5 5 4 8 7 5 5 10 7 8 7 8 8 8 10 8 8 11 9 11 2. I grew up in a very tiny town in the Midwestern United States. The two had seven streets, and the number of buildings on each street were a

Data Error

In the process of acquiring data for research, we sometimes find ourselves facing possibility that field workers may have intentionally introduced error into the data. (A) Why and how might they have done this? (B) What can we do to prevent such errors?

Standard Deviant - How Large of a Sample

A researcher is interested in the average amount of sugar that kindergarten kids eat per day within 4 grams. In a preliminary sample of 36 kids, the amount consumed ranged from 105 grams to 305 grams. The researcher wants to be 97% confident that the margin of error will not be exceeded. How large of a sample must she do if she

Range, Std. dev., and Variance

The number of cars that travel through an intersection between noon and 1pm is measured for 30 consecutive days. The results of the 30 observations are: 61,62,63,63,64,64,66,66,67,68,68,68,68,69,69,69,69,70,70,70,70,71,71,72,73,74,74,75,76,and 79 Find: a.) Range b.) Standard Deviation c.) The population standar

Box and Whisker Plots

A box and whisker plot is used to display data. Explain what box and whisker plots shows us. Provide example. Thanks.

Portfolio: expectation, standard deviation and covariance

An investor wants to invest 1000 euro. He can choose between the shares of the electronic company Solips and the food supply chain Bhold. The value of the first share is 1 euro at the moment the investment is made, the price of the second share is 2 euro. How should the investor divide the 1000 euro between the two types of shar