- Fudge requires a fairly strict adherence to the sequence of boiling sugar in milk until it reaches a certain consistency and then beating the mixture while it cools so that it acquires a smooth,
- After the report in For Example: "Capability indices for fudge production," the candy company makes some changes to the pouring process and wants the mean now to be \(18.15 \mathrm{oz}\). and the
- The price of a jewellery diamond depends on the 4 C's: carat weight, cut, clarity, and colour. Diamond colours are assigned letters from D, for colourless stones, through \(\mathrm{K}\), for
- Some true diamonds are coloured from inclusions or structural differences. Can the prices of these diamonds be predicted with the models we make for traditional clear diamonds?One website lists a
- The U.S. Geological Survey reports facts about a range of mineral and material commodities (minerals.usgs.gov/ds/2005/140/) including gemstones. From their report, we find that imports of gemstones
- When we first looked at diamond prices (in For Example: "Diamond prices"), we noted that we needed to model prices for different coloured diamonds separately. In other examples, we restricted our
- A large clothing store has recently sent out a special catalogue of fall clothes, and Leiram, its marketing analyst, wants to find out which customers responded to it and which ones bought the most.
- In the regression model of Respond Amount in For Example: "The multiple regression model for customer response to marketing," interpret the intercept and the regression coefficients of the three
- Here are plots of Respond Amount against the three predictors, a plot of the residuals against the predicted values from the multiple regression, a histogram of the residuals, and a Normal
- Leiram tries another model, adding the variable Age to see if that improves the model:Response Variable: Respond Amount\(R^{2}=91.50 \%:\) Adjusted \(R^{2}=91.23 \%\)\(s_{e}=18.179\) with
- In Chapter 19 we looked at data on the prices of diamonds (For Example: "Diamond prices"). Although higher carat weight of diamonds generally means higher cost, Carat Weight isn't the only factor
- After adding the indicator variables for Colour, which showed different intercepts for the three different colour levels, an analyst wonders if the slopes for the three colour levels might be
- Two other measures of quality of a diamond (see For Example: "Indicator variables for diamond colour") are its Table size and Deptb; both are expressed as percentages. Table size is the ratio of the
- In addition to the predictor variables from the last example (For Example: "Regression diagnostics for diamond prices"), we have information on the quality of the Cut (four grades: Good, Very Good,
- Commercial traffic between Canada and Alaska can be of great interest to businesses that ship to and from Alaska and to economists and investors concerned with those businesses. Here are the border
- The euro is the second-most traded currency (after the U.S. dollar), so its value relative to other currencies is of great interest. One euro was equal to one U.S. dollar when the new European
- Find and interpret a multiple regression model for the Canada-Alaska truck border crossing data from For Example: "Truck border crossings between Canada and Alaska." (The data are in the file Trucks.)
- Is the model for Alaska truck border crossings in For Example: “A regression model for truck border crossings” an additive or a multiplicative model? Describe the components. Which month was left
- State the Type I and Type II errors in complete sentences given the following statements.a. The mean number of years Americans work before retiring is 34.b. At most 60% of Americans vote in
- Here are more proposed survey questions for the survey mentioned in Exercise 13:Question 3: Do you find that the slow speed of dial-up internet access reduces your enjoyment of web services?Question
- A professional Canadian polling company recruits an “online panel” of people who agree to answer many surveys during the course of a year, in return for a financial reward. The surveys are
- A Canadian courier company is planning to introduce electric delivery trucks. It selects 5 cities at random out of all the cities in Canada where it operates and replaces its diesel delivery trucks
- The Canadian Environmental Assessment Agency took soil samples at 16 locations near a former industrial waste dump and checked each for evidence of toxic chemicals. The researchers found no elevated
- Inspectors send trained “renters” of various races and ethnic backgrounds, and of both sexes, to inquire about renting randomly assigned advertised apartments. They look for evidence that
- A company packaging snack foods maintains quality control by randomly selecting 10 cases from each day’s production and weighing the bags. Then the quality control staff open one bag from each case
- Prior to the mayoral election discussed in Exercise 27, the local newspaper conducted a poll. The paper surveyed a random sample of registered voters stratified by political party, age, sex, and area
- Prior to the mayoral election discussed in Exercise 27, the local newspaper conducted a poll. The paper surveyed a random sample of registered voters stratified by political party, age, sex, and area
- A cable TV company is considering offering optical fibre to residences to improve the speed of its movie download service. Before launching the new service, however, the company wants to find out
- Fisheries and Oceans Canada operates a laboratory in Sault Ste. Marie, Ontario, to study the abundance of species of fish that have invaded the Great Lakes from other ecosystems. Researchers have
- Here are more proposed questions for the survey in exercise 13.Question 3: Many people in Fapan have optical fibre connected to their homes. Should it be made available to you?Question 4: Since
- A particular brand of tires claims that its deluxe tire averages at least 50,000 miles before it needs to be replaced. From past studies of this tire, the standard deviation is known to be 8,000. A
- Trucks pass an automatic scale that monitors 2,000 trucks. This population of trucks has an average weight of 20 tons with a standard deviation of 2 tons. If a sample of 50 trucks is taken, what is
- The power of a test is 0.981. What is the probability of a Type II error?
- A question is asked of a class of 200 freshmen, and 23% of the students know the correct answer. If a sample of 50 students is taken repeatedly, what is the standard deviation of the mean of the
- A game is played repeatedly. A player wins one-fifth of the time. If samples of 40 times the game is played are taken repeatedly, what is the expected value of the mean of the sampling distribution
- A virus attacks one in three of the people exposed to it. An entire large city is exposed. If samples of 70 people are taken, what is the expected value of the mean of the sampling distribution of
- A virus attacks one in three of the people exposed to it. An entire large city is exposed. If samples of 70 people are taken, what is the standard deviation of the mean of the sampling distribution
- A company inspects products coming through its production process, and rejects detected products. One-tenth of the items are rejected. If samples of 50 items are taken, what is the expected value of
- A company inspects products coming through its production process, and rejects detected products. One-tenth of the items are rejected. If samples of 50 items are taken, what is the standard deviation
- A fishing boat has 1,000 fish on board, with an average weight of 120 pounds and a standard deviation of 6.0 pounds.If sample sizes of 50 fish are checked, what is the probability the fish in a
- An experimental garden has 500 sunflowers plants. The plants are being treated so they grow to unusual heights. The average height is 9.3 feet with a standard deviation of 0.5 foot. If sample sizes
- A company has 800 employees. The average number of workdays between absence for illness is 123 with a standard deviation of 14 days. Samples of 50 employees are examined. What is the probability a
- A maker of yardsticks has an ink problem that causes the markings to smear on 4% of the yardsticks. The daily production run is 2,000 yardsticks. What is the probability if a sample of 100 yardsticks
- A college gives a placement test to 5,000 incoming students each year. On the average 1,213 place in one or more developmental courses. If a sample of 50 is taken from the 5,000, what is the
- A researcher looks at a large set of data, and concludes the population has a standard deviation of 40. Using sample sizes of 64, the researcher is able to focus the mean of the means of the sample
- A company has 1,000 employees. The average number of workdays between absence for illness is 80 with a standard deviation of 11 days. Samples of 80 employees are examined. What is the probability a
- A maker of greeting cards has an ink problem that causes the ink to smear on 7% of the cards. The daily production run is 500 cards. What is the probability that if a sample of 35 cards is checked,
- Suppose X ~ N(–1, 2). What is the z-score of x = 2?
- An experiment with a probability of success given as 0.40 is repeated 100 times. Use the normal distribution to approximate the binomial distribution, and find the probability the experiment will
- An experiment with a probability of success given as 0.30 is repeated 90 times. Use the normal distribution to approximate the binomial distribution, and find the probability the experiment will have
- An experiment with a probability of success given as 0.40 is repeated 100 times. Use the normal distribution to approximate the binomial distribution, and find the probability the experiment will
- An experiment with a probability of success given as 0.30 is repeated 90 times. Use the normal distribution to approximate the binomial distribution, and find the probability the experiment will have
- An experiment with a probability of success given as 0.40 is repeated 100 times. Use the normal distribution to approximate the binomial distribution, and find the probability the experiment will
- An experiment with a probability of success given as 0.30 is repeated 90 times. Use the normal distribution to approximate the binomial distribution, and find the probability the experiment will have
- A multiple choice test has a probability any question will be guesses correctly of 0.25. There are 100 questions, and a student guesses at all of them. Use the normal distribution to approximate the
- A multiple choice test has a probability any question will be guesses correctly of 0.25. There are 100 questions, and a student guesses at all of them. Use the normal distribution to approximate the
- Thuy Dau, Ngoc Bui, Sam Su, and Lan Voung conducted a survey as to how long customers at Lucky claimed to wait in the checkout line until their turn. Let X = time in line. Table 6.1 displays the
- Suppose that the value of a stock varies each day from \($16\) to \($25\) with a uniform distribution.a. Find the probability that the value of the stock is more than \($19.b.\) Find the probability
- Suppose that you have at your disposal the information below for each of 30 drivers. Propose a model (including a very brief indication of symbols used to represent independent variables) to explain
- You want to buy a specific computer. A sales representative of the manufacturer claims that retail stores sell this computer at an average price of \($1,249\) with a very narrow standard deviation of
- In order to have a correlation coefficient between traits A and B, it is necessary to have:a. one group of subjects, some of whom possess characteristics of trait A, the remainder possessing those of
- Define the Correlation Coefficient and give a unique example of its use.
- If the correlation between age of an auto and money spent for repairs is +.90a. 81% of the variation in the money spent for repairs is explained by the age of the autob. 81% of money spent for
- Suppose that college grade-point average and verbal portion of an IQ test had a correlation of .40. What percentage of the variance do these two have in common?a. 20b. 16c. 40d. 80
- True or false? If false, explain why: The coefficient of determination can have values between -1 and +1.
- True or False: Whenever r is calculated on the basis of a sample, the value which we obtain for r is only an estimate of the true correlation coefficient which we would obtain if we calculated it for
- Under a "scatter diagram" there is a notation that the coefficient of correlation is .10. What does this mean?a. plus and minus 10% from the means includes about 68% of the casesb. one-tenth of the
- The correlation coefficient for X and Y is known to be zero. We then can conclude that:a. X and Y have standard distributionsb. the variances of X and Y are equalc. there exists no relationship
- What would you guess the value of the correlation coefficient to be for the pair of variables: "number of man-hours worked" and "number of units of work completed"?a. Approximately 0.9b.
- In a given group, the correlation between height measured in feet and weight measured in pounds is +.68. Which of the following would alter the value of r?a. height is expressed centimeters.b. weight
- Define a t Test of a Regression Coefficient, and give a unique example of its use.
- The correlation between scores on a neuroticism test and scores on an anxiety test is high and positive; thereforea. anxiety causes neuroticismb. those who score low on one test tend to score high on
- True or False? If False, correct it: Suppose a 95% confidence interval for the slope β of the straight line regression of Y on X is given by -3.5 < β < -0.5. Then a two-sided test of the hypothesis
- True or False: It is safer to interpret correlation coefficients as measures of association rather than causation because of the possibility of spurious correlation.
- We are interested in finding the linear relation between the number of widgets purchased at one time and the cost per widget. The following data has been obtained: X: Number of widgets purchased - 1,
- Discuss briefly the distinction between correlation and causality.
- True or False: If r is close to + or -1, we shall say there is a strong correlation, with the tacit understanding that we are referring to a linear relationship and nothing else.
- Consider a sample least squares regression analysis between a dependent variable (Y) and an independent variable (X).A sample correlation coefficient of −1 (minus one) tells us thata. there is no
- In correlational analysis, when the points scatter widely about the regression line, this means that the correlation isa. negative.b. low.c. heterogeneous.d. between two measures that are unreliable.
- In a linear regression, why do we need to be concerned with the range of the independent (X) variable?
- Suppose one collected the following information where X is diameter of tree trunk and Y is tree height. Y 48 24 8 18 6 22 10 30 68 Table 13.3 Regression equation: y; = -3.6 + 3.1. Xi What is your
- The manufacturers of a chemical used in flea collars claim that under standard test conditions each additional unit of the chemical will bring about a reduction of 5 fleas (i.e. where X j = amount of
- True or False? If False, correct it: Suppose you are performing a simple linear regression of Y on X and you test the hypothesis that the slope β is zero against a two-sided alternative. You have n
- An economist is interested in the possible influence of "Miracle Wheat" on the average yield of wheat in a district. To do so he fits a linear regression of average yield per year against year after
- An interpretation of r = 0.5 is that the following part of the Y-variation is associated with which variation in X:a. mostb. halfc. very littled. one quartere. none of these
- Which of the following values of r indicates the most accurate prediction of one variable from another?a. r = 1.18b. r = −.77c. r = .68
- A computer program for multiple regression has been used to fit Part of the computer output includes:a. Calculation of confidence interval for b2 consists of _______± (a student's t value)
- An investigator has used a multiple regression program on 20 data points to obtain a regression equation with 3 variables. Part of the computer output is:a. 0.80 is an estimate of ___________.b. 0.10
- Name one assumption that must be true.There are two assumptions that must be true in order to perform an F test of two variances.
- What is the other assumption that must be true?There are two assumptions that must be true in order to perform an F test of two variances.
- State the null and alternative hypotheses.Two coworkers commute from the same building. They are interested in whether or not there is any variation in the time it takes them to drive to work. They
- What is s1 in this problem?Two coworkers commute from the same building. They are interested in whether or not there is any variation in the time it takes them to drive to work. They each record
- What is s2 in this problem?Two coworkers commute from the same building. They are interested in whether or not there is any variation in the time it takes them to drive to work. They each record
- What is n?Two coworkers commute from the same building. They are interested in whether or not there is any variation in the time it takes them to drive to work. They each record their times for 20
- What is the F statistic?Two coworkers commute from the same building. They are interested in whether or not there is any variation in the time it takes them to drive to work. They each record their
- Is the claim accurate?
- State the null and alternative hypotheses.Two students are interested in whether or not there is variation in their test scores for math class. There are 15 total math tests they have taken so far.
- What is the F Statistic?Two students are interested in whether or not there is variation in their test scores for math class. There are 15 total math tests they have taken so far. The first
- What is the critical value?Two students are interested in whether or not there is variation in their test scores for math class. There are 15 total math tests they have taken so far. The first
- At the 5% significance level, do we reject the null hypothesis?Two students are interested in whether or not there is variation in their test scores for math class. There are 15 total math tests they

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