ECON 221 Test 2

A market research company employs a large number of typists to enter data into a computer database. The time it takes for potential new typists to learn the computer system is known to have a Normal distribution with a mean of 90 minutes and a standard deviation of 18 minutes. A candidate is automatically hired if she learns the computer system in less than 100 minutes. A cutoff time is set at the slowest 10% of the learning distribution. Anyone slower than this cutoff time is definitely not hired. What proportion of candidates take more than 2 hours to learn the computer system?

A) 0.048 B) 0.452 C) 0.711 D) 0.952 Answer: A

Using the standard Normal distribution tables, what is the area under the standard normal curve corresponding to Z> -1.22?

A) 0.1151 B) 0.1112 C) 0.8849 D) 0.8888 Answer: D

Using the standard Normal distribution tables, what is the area under the standard normal curve corresponding to Z<1.1?

A) 0.1357 B) 0.2704 C) 0.8413 D) 0.8643 Answer: D

Many residents of suburban neighborhoods own more than one car but consider one of their cars to be the main family vehicle. The age of these family vehicles can be modeled by a normal distribution with a mean of 2 years and a standard deviation of 6 months. What is the standardized value for a family vehicle that is 3 years and 3 months old?

A) 0.22 B) 2.5 C) 2.6 D) 2.92 Answer: B

Using the standard Normal distribution tables, what is the area under the standard Normal curve corresponding to - 0.5 < Z < 1.2?

A) 0.3085 B) 0.8849 C) 0.5764 D) 0.2815 Answer: C

The temperature at any random location in a kiln used for manufacturing bricks is Normally distributed with a mean of 1000 degrees F and a standard of 50 degrees F. When glazed bricks are put in the oven, if the temperature is below 900 degrees F, they will discolor. If the bricks are placed randomly throughout the kiln, what percent of glazed bricks will discolor?

A) 0.62% B) 2.28% C) 47.72% D) 49.38% Answer: B

As part of a large ongoing study on the treatment of women with breast cancer, the treatment time (in months) of eight patients whose lymph nodes were cancer-free is recorded. Treatment time is defined as the time from the moment the cancer treatment starts until the patient is declared cancer -free. 9.47, 8.60, 19.33, 16.33, 8.50, 9.40, 17.67, 9.30 What is the mean treatment time for these eight women?

A) 10.5 months B) 11.67 months C) 12.325 months D) 15 months Answer: C

In class, we analyzed dataset TTS24 from the textbook. What is the median time to start a business for the 24 countries (without Venezula)?

A) 12 days B) 14 days C) 13 days D) 15 days Answer: C

The asking prices (in thousands of dollars) for a sample of 13 houses currently on the market in Neighborville are listed below. For convenience, the data have been ordered. 175, 199, 204, 234, 259, 275, 299, 304, 317, 345, 355, 384, 549 What is the five number summary?

A) 125, 234, 290, 345, 549 B) 175, 234, 299, 345, 549 C) 175, 219, 299, 350, 549 D) None of the above Answer: C

High levels of glucose in the blood are indicative of diabetes, which is becoming more prevalent in the United States. Diabetes can lead to many complications, such as blindness and heart disease. A random sample of 180 individuals had their blood sugar levels measured. The five-number summary is given below. 52, 79, 91, 119, 220 How many of the people in the sample had glucose levels above 119?

A) 135 B) 25 C) 45 Answer: C

In class, we built vertical side-by-side boxplots to show the relationship between the length of writers' lives and the type of literary work they did. Which command did we use?

A) boxplot (data$Age ~ data$Type, horizontal = TRUE) B) boxplot (data$Age ~ data$Type) C) plot (data$Age ~ data$Type, type = "box") D) boxplot (type ~ Age, data = data) Answer: B

in class, we created a horizontal boxplot in R using data on the lengths of writers' lives. Which command did we use to build the horizontal boxplot?

A) boxplot( Age ~ data, horizontal =TRUE) B) boxplot (data$Age, horizontal = FALSE) C) boxplot (data$Age, horizontal = TRUE) D) plot (data$Age, type="box", horizontal = TRUE) Answer: C

Consider the following stemplot. In the stemplot, 2|8 represents 28. 16, 22, 24, 28, 29, 30, 31, 31, 32, 33, 36, 37, 38, 40, 45, 48, 50, 51, 58, 61 The mean of the data represented in this stemplot:

A) is 34.5 B) is 37 C) cannot be computed from the information given Answer: B

The ages (to the nearest year) of the 667 people participating in a large workshop are summarized as shown below. Age: 18, 19, 20, 21, 22, 23, 24, 25, 32 Number of Students: 14, 120, 200, 200, 90, 30, 10, 2, 1 what is true about the median age?

A) it could be any number between 19 and 20 B) it must be twenty C) it must be 21 D) it must be over 21 Answer: B

According to the 1.5 X IQR rule, what would make the value 127 a suspected outlier in the PTH data ( we studied in class and analyzed in the textbook)?

A) it falls below the first quartile B) it is more than 1.5 X IQR above the third quartile C) It is more than 1.5 X IQR below the minimum value D) It is greater than the maximum value in the data set Answer: B

Which of the following is a characteristic of the interquartile range (IQR)?

A) it is sensitive to extreme values B) it measures the range of the entire data set C) it describes the spread of the central 50% of the data D) it is the difference between the smallest and largest observations Answer: C

Why is the mean considered a non-resistant measure of center?

A) it requires manual addition and division to compute B) it is not influenced by outliers C) it always equals one of the data points in the set D) it is sensitive to extreme observations or outliers Answer: D

based on what we studied in class for PTH data (see example 1.26 in the textbook), why was the PTH measurement of 127 pg/ ml considered an outlier?

A) it was within the normal range of values for the PTH B) it was the lowest value recorded and inconsistent with other measurements C) it was consistent with measurements taken on a different day D) it was the highest value recorded and inconsistent with other measurements Answer: D

Given the following student scores dataset: 75, 87, 94, 85, 74, 98, 93, 52, 80, 91, what is the five number summary for this data set?

A) minimum: 52, Q1: 74, Median: 86, Q3: 94, Maximum: 98 B) minimum: 52, Q1: 75, Median: 85, Q3: 93, Maximum: 98 C) Minimum: 52, Q1: 75, Median: 86, Q3: 93, maximum: 93 D) Minimum: 52, Q1: 80, Median: 87, Q3: 94, Maximum: 98 Answer: C

A quantile plot of the horsepower of a sample of 65 cars is shown below. Which of the following descriptions best describes the shape of the distribution of horsepower?

A) normal B) normal with some outliers C) left-skewed D) right- skewed Answer: C

For a physics course containing 11 students, the maximum point total for the quarter was 200. The point totals for the 11 students are given in the stemplot below. Which of the following statements is true?

A) since there are 7 stems, the median must be contained in the fourth smallest steam and be between 140 and 150 B) because of the small sample size, it would be impossible to split the stems in this stemplot. C) we can compute the mean number of points for the 11 students from the information in the stemplot. Answer: C

A distribution has a mean of 100 and a median of 120. The shape of this distribution is most likely to be:

A) skewed right B) symmetric C) Skewed left Answer: C

what is the shape of the distribution of business start times based on the stemplot?

A) skewed to the right B) symmetric C) skewed to the left D) bimodal Answer: A

What does the standard deviation measure?

A) the center of a distribution B) the spread of observation from their mean C) the average of all data points D) the median of a distribution Answer: B

what does a time plot primarily show?

A) the distribution of a variable without considering time B) the correlation between two variables C) each observation against the time it was measured D) the summary statistics of the data Answer: C

A reporter wishes to portray baseball players as overpaid. Which measure of center should he report as the average salary of major league players?

A) the mean B) the median C) either the mean or median - they will be equal in this case D) neither the mean nor the median - both will be much lower than the actual average salary.

For the density curve below, which of the following statements is TRUE?

A) the mean and median are equal B) the mean is greater than the median C) the mean is less than the median D) the mean could be either greater than or less than the median Answer: C

Which of the following statements about the mean and the median of a density curve is FALSE?

A) the median is the point on the axis that divides the area under the density curve is two equal halves B) the median and the mean have the same value if the density curve is symmetric C) the mean is the "balance point" of the density curve D) the median of a skewed density curve is pulled away from the mean in the direction of the long tail E) for a symmetric density curve, both the mean and the median are at the center of the curve Answer: D

What does the formula (n+1)/2 represent in calculating the median?

A) the position of the median in the ordered list B) the exact value of the median C) the average of all observations D) the mode of the distribution Answer: A

In class and in the textbook we considered data on IQ scores of 60 high school students (fig 1.13 in the textbook). What feature of the boxplot suggests that the distribution of IQ scores is symmetric?

A) the quartiles are equally spaced from the median B) the mean is higher than the median C) the whiskers are of different lengths D) the histogram shows a skewed distribution Answer: A

What happens when deviations are squared in the context of variance?

A) the sum of deviations becomes zero B) negative deviations become positive C) only large deviations affect the variance D) deviations are ignored Answer: B

What does the bar over the x in x(bar) represent?

A) the total sum of all observations B) the middle value of the observations C) the mean of all observations D) the difference between the maximum and minimum values Answer: C

Which of the following statements about the standardized z-score of a value of a variable X, which has a mean of m and a standard deviation of S, is (are) true?

A) the z-score has a mean equal to 0 B) the z-score has a standard deviation equal to 1 C) the z-score tells us how many standard deviation units from the original observation fall away from the mean D) the z-score tells us the direction in which an observation falls away from the mean E) all of the above statements about the z-score are true Answer: E

the five number summary of scores on a test is given below. 35, 60, 65, 70, 90 Based on this information:

A) there are low outliers B) there are no outliers C) there are both high and low outliers Answer: C

Which of the following best describes the purpose of the modified boxplot?

A) to identify outliers using the 1.5 X IQR rule B) to illustrate the mean of a dataset C) to show only the median and quartiles Answer: A

Why is it suggested to round the mean time to start a business to 19 days?

A) to show greater accuracy in the data B) to focus on meaningful digits and provide practical information C) to increase the number of decimal places D) to match the data set's precision Answer: B

A sample was taken of 20 salaries of employees in a large company. The following are the annual salaries (in thousands of dollars). For convenience, the data have been ordered. 28, 31, 34, 35, 37, 41, 42, 42, 42, 47, 49, 51, 52, 52, 60, 61, 67, 72, 75, 77 What is the interquartile range of the 20 salaries?

21500 Do the median and then do the cut off and find the Q3 and Q1 values. From there: Q3 - Q1 = interquartile range

A tool and die company has been contracted to produce metal castings into which a hole is to be drilled to a diameter of 2.5 centimeters. Because of the variability in the drilling process, the actual diameter of the hole is a normally distributed variable with a mean of 2.5 centimeters and a standard deviation of 0.1 centimeters. The proportion of castings produced by this process with a hole whose diameter is within 0.2 centimeters of the desired value is

A) 0.9772 B) 0.9549 C) 0.9974 D) 0.6826 E) 0.0228 Answer: B

A well-known maker of jams and jellies packages its jars labeled "250 milliliters." The process used to fill the jars is known to dispense an amount of jam that is a normally distributed variable with u = 252 milliliters and sigma = 0.9 milliliters. What proportion of jars will be filled with what the label claims is 250 milliliters?

A) 0.9868 B) 0 C) 0.0068 D) 0.0132 E) 0.0027 Answer: B

The following curve is to be a density curve for the variable X. What must be the value of the point on the vertical axis labeled H for this to be a proper density function?

A) 1.60 B) 1.00 C) 0.80 D) 1.25 E) 0.625 Answer: D

data: metabolic rates (calories per 24 hours) of seven men: 1792, 1666, 1362, 1614, 1460, 1867, 1439 What is the standard deviation of the metabolic rates calculated?

A) 150.00 Calories B) 189.24 Calories C) 200.00 Calories D) 160.00 Calories Answer: B

In class after adding Venezula, which has a start time of 230 days, to the previous sample, the mean for the 25 countries changes. What is the new mean with two decimal points? (Hint: this question is motivated by check-in question 1.16 in the textbook which uses TTS25 dataset attached in the textbook to make this calculation.)

A) 26.88 days B) 27.08 days C) 27.32 days D) 27.00 days Answer: C

The following boxplot represents the birth weights (in ounces) of 160 infants born in a local hospital. Approximately ___________ children has birth weights between 102 and 122 ounces.

A) 40 B) 50 C) 80 D) 100 Answer: C

During the early part of the 1994 baseball season, many sports fans and baseball players noticed that the number of home runs being hit seemed to be unusually large. The numbers of home runs by American League and National League teams, based on the team by team statistics on home runs hit through Friday, June 3, 1994, are given below (from the Columbus Dispatch, Sunday, June 5, 1994). American League 35, 40, 43, 49, 51, 54, 57, 58, 58, 64, 68, 68, 75, 77 National League 29, 31, 42, 46, 47, 48, 48, 53, 55, 55, 55, 63, 63, 67 What is the mean number of home runs hit by American League teams?

A) 48.5 B) 56.9 C) 57.5 D) 58.1 Answer: B

The scores on the survey of study habits and attitudes (SSHA) for a sample of 150 first year college women produced the following boxplot and descriptive statistics using MINITAB. The number of women with scores between 93.26 and 129.23 is about:

A) 50 B) 75 C) 36 Answer: 75

Items produced by a manufacturing process are supposed to weigh 90 grams. However, there is variability in the items produced, and they do not all weigh exactly 90 grams. The distribution of weights can be approximated by a normal distribution with a mean of 90 grams and a standard deviation of 1 gram. What percentage of the items will weigh either less than 87 grams or more than 93 grams?

A) 6% B) 94% C) 99.7% D) 0.3% Answer: D

Which of the following is NOT part of the five number summary?

A) Minimum B) First Quartile C) Mean D) Third Quartile E) Maximum Answer: C

What happens to Q3 if the highest value changes from 67 to 670?

A) Q3 remains the same B) Q3 decreases C) Q3 increases D) Q3 becomes undefined Answer: A

The exam scores of 10 students are: 75, 87, 94, 85, 74, 98, 93, 52, 80, 91 Based on the 1.5 X IQR rule for outliers, how low would the lowest score need to be for it to be considered an outlier?

A) less than 40.00 B) less than 44.25 C) less than 48.00 D) less than 49.75 Answer: C

Which of the following is used to identify outliers in a dataset?

A) median B) mean C) standard deviation D) 1.5 X IQR Rule Answer: D

Which density curve below has the largest standard deviation?

Mean: 0 St. Deviation: 1 prob ( x < = 3) = 0.9986501

For the density curve displayed below, what is the mean?

A) 0.25 B) 0.50 C) 0.71 D) 0.75 Answer: B

In class we analyzed dataset from the textbook TTS25. Including Venezuela, with a start time of 230 days, in the dataset shows the median is 14 days. What is the effect of the outlier on the median?

1) it increases the median significantly 2) it decreases the median significantly 3) it has little to no effect on the median Answer: 3

What is the primary reason the mean endowment is much higher than the median endowment for colleges?

1) the mean is close to the typical value for all institutions 2) a few wealthy institutions pull the mean higher, while the medina is resistant to extreme values 3) the median is affected by the long tail of extreme values Answer: 2

What happens when a large outlier is added to a data set?

1) the median remains almost the same, but the mean increases significantly 2) both the mean and median increase by a large amount 3) the mean remains almost the same, but the median increases significantly Answer: 1

Suppose the sample size is 35. Where is the median located?

1) 15th observation 2) 16th observation 3) 17th observation 4) 18th observation Answer: 4

Here are the scores on the first exam in an introductory statistics course for 10 minutes: 75, 87, 94, 85, 74, 98, 93, 52, 60, 80 what is the median exam score?

1) 86 2) 85 3)82.5 4) 87 Answer: 3

How do quartiles divide a data set?

1) into four equal parts, each containing 25% of the data 2) into three equal parts 3) into two equal parts Answer: 1

How can a stemplot help in computing the median?

1) it allows you skip finding the median's location 2) it automatically provides the median value 3) it shows both median and the mean 4) the data is already ordered, so you can count to the median's position Answer: 4

Insurance Institute for Highway Safety publishes data on the total damage suffered by compact automobiles in a series of controlled, low-speed collisions. The costs for a sample of nine cars, in hundreds of dollars, are provided below. 10, 6, 8, 10, 4, 3.5, 7.5, 8, 9 What is the first quartile for the above data?

A) $350 B) $400 C) $600 D) none of the above Answer: D

Insurance Institute for Highway Safety publishes data on the total damage suffered by compact automobiles in a series of controlled, low-speed collisions. The costs for a sample of nine cars, in hundreds of dollars, are provided below. 10, 6, 8, 10, 4, 3.5, 7.5, 8, 9 What is the median cost of the total damage suffered for this sample of cars?

A) $400 B) $730 C) $800 D) $1000 Answer: C

The Insurance Institute for Highway Safety publishes data on the total damage suffered by compact automobiles in a series of controlled, low-speed collisions. The costs for a sample of nine cars, in hundreds of dollars, are provided below. 10, 6, 8, 10, 4, 3.5, 7.5, 8, 9 What is the interquartile range of the above data?

A) a value less than $200 B) A value between $200 and $460 C) A value between $460 and $800 D) None of the above Answer: B

The Michigan Department of Transportation (M-DOT) is working on a major project: 80% of the highways in Michigan need to be repaved. To speed the completion of this project, many contractors will be working for M-DOT. Contractors are currently bidding on the next part of the project. To help make a decision about which contractor to hire, M-DOT collects many variables besides just the estimated cost. One of those variables is the contractor's estimate of the number of workdays required to finish the job. Twenty contractors have bid on the next job. The boxplot below represents their estimates of the number of work days required. What is (approximately) the interquartile range, based on the boxplot?

A) 140 days B) 270 days C) 360 days D) 760 days Answer: B

A study was conducted on the distance that various brand-name golf balls would travel. The study involved the use of a standard testing machine and a seven iron. A selection of results from the study is given below for the distance (in yards) for each brand of ball. 144.0, 145.8, 138.7, 141.3, 142.8, 143.8, 145.8, 144.5 The mean x and the standard deviation s of these measurements (in yards) are, respectively:

A) 143.90 and 3.10 B) 143.34 and 2.39 C) 142.25 and 5.73 D) 143.34 and 2.24 E) 143.90 and 2.39 Answer: B

PTH values: 19, 25, 28, 28, 28, 30, 31, 31, 31, 33, 35, 38, 39, 40, 45, 46, 48, 49, 48, 50, 50, 59, 60, 60, 63, 64, 71, 71, 127 Which of the following is the correct five number summary for the PTH data?

A) 19, 30, 40, 55, 127 B) 20, 31, 45, 55, 130 C) 19, 31, 40, 54.5, 120 D) 19, 31, 45, 59.5, 127 Answer: D

In class a random sample of 24 countries was selected, excluding Venezuela (see example 1.20 in the textbook with attached in the textbook data TTS24). What was the mean "time to start" (in days) for these 24 countries (before adding Venezuela)?

A) 21.75 days B) 19.38 days C) 20.67 days D) 18.88 days Answer: D

A biology class has 201 students. The five number summary for the midterm exam is given below. 23, 51, 62, 78, 92 The student with the 92 found a grading error on her exam, and her correct grade was 95. There were no other grading errors. After this student's grade is corrected, the five-number summary for the midterm exam will be:

A) 23, 51, 62, 81, 95 B) 23, 51, 62, 78, 92 C) 23, 51, 62, 78, 95 Answer: C

For the density curve below, what percent of the observations lie between 0.5 and 1.2?

A) 25% B) 35% C) 50% D) 70% Answer: B

The environmental protection agency records data on the fuel economy of many different makes of cars. Data on the mileage of 20 randomly selected cars are listen below. The values are ordered for convenience. 12, 13, 15, 16, 16, 17, 18, 18, 19, 19, 20, 20, 22, 23, 24, 26, 26, 27, 27, 29 What is the interquartile range for the mileage?

A) 8.5 miles per gallon B) 16.5 miles per gallon C) 17 miles per gallon D) 25 miles per gallon Answer: A

Here are the scores on the first exam in an introductory statistics course for 10 students: 75, 87, 94, 85, 74, 98, 93, 52, 80, 91 What is the mean first exam score for these students?

A) 82.4 B) 83.5 C) 82.9 D) 85.5 Answer: C

The numbers of Facebook friends that students at a university have are normally distributed with a mean of 1200 and a standard deviation of 200. What percent of the students have exactly 1000 Facebook friends?

A) 84.13% B) 15.86% C) 42.07% D) None of the above Answer: D

The numbers of Facebook friends that students at a university have are normally distributed with a mean of 1200 and a standard deviation of 200. What percent of the students have at least 1000 Facebook friends?

A) 84.13% B) 15.86% C) 42.07% D) None of the above Answer: A

The following boxplot represents the birth weights (in ounces) of 160 infants born in a local hospital. About 40 of the birthweights were below ________.

A) 92 ounces B) 102 ounces C) 112 ounces D) 122 ounces Answer: B

Which of the following correctly describes the components of a boxplot?

A) A central box spans the mean and the range, with lines extending to the median and extremes. observations B) a central box spans the median and the mode, with the lines extending to the quartiles and extremes C) A central box spans the quartiles Q1 and Q3, with a line for the median and whiskers extending to the smallest and largest D) a central box spans the median and the smallest observation, with lines extending to the quartiles and the largest observation Answer: C

Which of the following statements about a density curve is FALSE?

A) A density curve always has an area beneath it equal to 1 B) a density curve can adequately describe outliers observed in data C) A density curve is always on or above the horizontal axis D) A density curve comes in many shapes, some of which are symmetric while others are skewed E) the area under a density curve above any range of values is the proportion of all observations that fall in that range. Answer: B

Agricultural fairs often hold competitions for produce grown by local gardeners. The following data are the weights ( in pounds) of tomatoes entered into an annual fair in Roland, Mantioba, Canada in 2007. 2.48, 1.52, 1.15, 1.13, 1.00, 0.99, 0.96, 0.94, 0.75 The interquartile range (IQR) for these data is:

A) A value less than 0.40 pound B) A value between 0.50 pound and 0.60 pound C) A value between 0.65 pound and 0.75 pound D) A value greater than 0.80 pound Answer: A

Which of the following do not adequately reveal outliers?

A) Density curves B) Stemplots C) histograms D) modified boxplots Answer: A

Consider the following scores on the first exam in an introductory statistics course for 10 students: 52, 74, 75, 80, 85, 87, 91, 93, 94, 98 Find its location of the median of the first half of the data (Q1) and its value.

A) Location: 2.5, value: 74.5 B) Location: 3, Value: 75 C) Location: 2, Value: 75.5 D) Location: 4, Value: 80.5 Answer: B

Consider the following scores on the first exam in an introductory statistics course for 10 students: 52, 74, 75, 80, 85, 87, 91, 93, 94, 98 Find the location of the median (M) and its value.

A) Location: 5, Value: 85 B) Location: 6, Value: 87 C) Location: 5.5, Value: 87 D) Location: 5.5, Value: 86 Answer: D

Consider the following scores on the first exam in an introductory statistics course for 10 students: 52, 74, 75, 80, 85, 87, 91, 93, 94, 98 Find the location of the median of the second half of the data (Q3) and its value.

A) Location: 8, Value: 91 B) Location: 7.5, Value: 92 C) Location: 8, Value: 93 D) Location: 7, Value: 91 Answer: C

According to the boxplots in Example 1.27 (from the textbook and which we built in R using dataset POETS from the textbook), which group tends to live the longest?

A) Novelists B) Poets C) Nonfiction writers D) All groups live equally long Answer: C

At a Canadian agricultural fair held in Neguac, New Bruinswick, giant pumpkins were entered into a competition. The following stem and leaf plot of the weight (in pounds) of the 35 pumpkins in the competition was constructed, where, for example, 9|$ represents 940 pounds. 90, 100, 130, 170, 180, 240, 240, 290, 320, 320, 410, 420, 430, 460, 460, 470, 490, 530, 560, 560, 590, 600, 610, 620, 620, 660, 690, 710, 760, 800, 900, 940, 1080, 1190 The quartilesQ1 and Q4 for these data are:

A) Q1 = 90 and Q3 = 1190 B) Q1 = 320 and Q3= 640 C) Q1 = 322 and Q3 = 716 D) Q1 = 320 and Q3 = 660 E) Q1 = 490 and Q3 = 660 Answer: D

In class, we created a time plot in Excel to show the women's marathon time records from the 1970s to the present. What steps did we follow to create the chart?

A) we left the titles of both columns A and B and then went to the Insert tab and chose a line chart B) we deleted the title of the first variable showing the year of the record to signal to Excel that this variable should represent time values on the horizontal axis. Then, we selected both columns A and B, went to the insert tab, and chose a line chart C) we highlighted only the column with the years, went to the insert tab, and selected a bar chart D) we entered the data in a single column, went to the insert tab, and selected a scatter plot Answer: B

According to the 1.5 X IQR rule, when is an observation considered a suspected outlier?

A) when it falls more than 1.5 times the IQR above the third quartile or below the first quartile B) when it falls more than 1.5 times the IQR below the minimum C) When it is outside the range of the entire dataset D) When it falls below the median or above the mean Answer: A

The variable Z has a standard normal distribution. Find the value Z such that 85% of the observations fall below z.

A) z = -1.04 B) z = 0.80 C) z = 0.85 D) z = 1.04 Answer: D

The variable Z has a standard normal distribution. Find the value Z such that the event Z> z has proportion of 0.08.

A) z = -1.41 B) z = 0.53 C) z = 0.82 D) z = 1.41 Answer: D

The time to complete an exam is approximately Normal with a mean of 70 minutes and a standard deviation of 10 minutes. Using the 68-95-99.7 rule, what percent of students will complete the exam in under an hour?

A)68% B)32% C)16% D)5% Answer: C

A sample was taken of 20 salaries of employees in a large company. The following are the annual salaries (in thousands of dollars). For convenience, the data have been ordered. 28, 31, 34, 35, 37, 41, 42, 42, 42, 47, 49, 51, 52, 52, 60, 61, 67, 72, 75, 77 What is the first quartile of the 20 salaries?

Answer: 39000

The Michigan Department of Transportation (M-DOT) is working on a major project: 80% of the highways in Michigan need to be repaved. To speed completion of this project, many contractors will be working for M-DOT. Contractors are currently bidding on the next part of the project. To help make a decision about which contractor to hire, M-DOT collects many variables besides just the estimated cost. One of those variables is the contractor's estimate of the number of workdays required to finish the job. Twenty contractors have bid on the next job. The boxplot below represents their estimates of the number of work days required. Select all of the following statements that are true:

True Statements: - the median number of days is approximately 180 - the minimum number of days is approximately 40 False Statements: - the maximum number of days is approximately 750 - twenty- five percent of contractors estimated the number of days to more than 100

select the true statement(s) regarding the density curve shown.

True statements: - the total area under the curve is 1 - the median is 1 - it is symmetric - the mean is 1