Babies 6 to 23 months of age with inner ear infections were given antibiotics. The children were randomly assigned to receive antibiotics for a full 10 days or to receive antibiotics for 5 days and then a placebo for 5 days. There were 229 children assigned the shorter course, and 77 of them had “clinical failure” whereas of the 238 assigned to the longer course of antibiotics, 39 had clinical failure. (Source: Hoberman et al., “Shortened antimicrobial treatment for acute otitis media in young children,” New England Journal of Medicine, vol. 375 [December 2016]: 2446–2456) a. Compare the percentage of clinical failure in each group and state which group did better. b. Create a two-way table with 10 days and 5 days across the top and failure and success down the left side. Fill in all four numbers. c. Was this an observational study or a controlled experiment? How do you know? d. Can you conclude that the treatment caused the difference? Why or why not?
> Refer to the accompanying bar chart, which shows the time spent on a typical day talking on the cell phone for some men and women. Each person was asked to choose the one of four intervals that best fit the amount of time he or she spent on the phone (fo
> The accompanying graph is a special histogram with additional information; it was made using StatCrunch. People who studied music as children were asked how many hours a day they practiced when they were teenagers, and whether they still play now that th
> The following graph shows the ages of females (labeled 1) and males (labeled 0) who are majoring in psychology in a four-year college. a. Is this a histogram or a bar graph? How do you know? b. What type(s) of graph(s) would be more appropriate?
> The pie chart reports the number of hours of sleep “last night” for 118 college students. What would be a better type of graph for displaying these data? Explain why this pie chart is hard to interpret.
> One of the authors wanted to determine the effect of changing answers on multiple-choice tests. She studied the tests given by another professor, who had told his students before their exams that if they had doubts about an answer they had written, they
> A sample of students were questioned to determine how much they would be willing to pay to see a movie in a theater that served dinner at the seats. The male students responded (in dollars): 10, 15, 15, 25, and 12. The female students responded: 8, 30, 1
> The following table gives the number of commercial U.S. radio stations for the four most popular formats. Sketch or otherwise create an appropriate graph of the distribution and comment on its important features. (Source: 2017 World Almanac and Book of F
> The following table gives the percent of the market controlled by the most popular Internet browsers in 2016. Sketch or otherwise create an appropriate graph of the distribution and comment on its important features. (Source: 2017 World Almanac and Book
> Data on the percentage of adults living in the United States who meet the federal aerobic fitness (AF) and muscle-strengthening (MS) standards are displayed in the bar plot. (Source: 2017 World Almanac and Book of Facts) a. Comment on the fitness similar
> Data on obesity rates for adults in the United States are displayed in the bar plot for three age groups. (Source: 2017 World Almanac and Book of Facts) a. Which age group typically has the highest rate of obesity? b. Comment on any similarities and diff
> The Bureau of Labor Statistics tracks data on the percentage of jobs that require various levels of education. The 2016 Entry Level Education data are displayed in the following bar chart and pie chart. a. Approximately what percentage of jobs require so
> Pew Research conducted a survey in 2017 asking gun owners what percentage of time they had a loaded gun easily within reach when at home. The results for male gun owners are displayed in a bar chart and a pie chart. a. Which period was the most frequent
> Applicants to California community colleges are asked to indicate one of these education goals at the time of application: transfer to a four-year institution, an AA degree, a CTE certificate, job retraining, or personal enrichment. In a group of 500 app
> Suppose a group of school-aged children is asked, “Which of these three ice cream flavors do you like the most: vanilla, chocolate, or strawberry?” Describe a bar graph of their responses that would have the least amount of variability. Also describe a b
> According to the World Health Organization (WHO), there are five leading causes of preventable deaths in the world. They are shown in the following graph. a. Estimate how many preventable deaths result from high blood pressure. b. Estimate how many preve
> A post office branch recorded the number of customers served per day for a period of time. The data are displayed in the following histogram and dotplot. Based on these graphs, would it be unusual for this branch to serve 250 customers in a day? Why or w
> Emmanuel, a student at a Los Angeles high school, kept track of the calorie content of all the snacks he ate for one week. He also took note of whether the snack was mostly “sweet” or “salty.” The sweet snacks: 90, 310, 500, 500, 600, 90 The salty snacks
> The resting pulse rates (in beats per minute) of a sample of 91 undergraduate students were recorded. The data are displayed in the following histogram and dotplots. Based on these graphs, would you consider a resting pulse rate of 90 beats per minutes t
> The histogram shown is for number of calories in a sample of fast-food items. (Source: Stat Crunch survey). a. What is the bin width of the histogram? b. Would this graph be best described as unimodal or bimodal? c. Approximately what percentage of the f
> The histogram shown is for pulse rates for125 people. Convert the vertical axis to relative frequency and show the value that would replace each of the values on the vertical axis. (Source: NHANES)
> A dotplot of the glucose readings from 132 people (from NHANES) is shown. Some doctors recommend that glucose readings not be above 120 mg/dl. a. How many of these people have glucose readings above 120 mg/dl? b. What percentage of these people have gluc
> The dot plot shown is for resting pulse rates of 125 people (according to NHANES, National Health and Nutrition Examination Survey). Many sources say the resting pulse should not be more than 100. a. How many of the 125 people had resting pulse rates of
> Data are available on the percent alcohol in 101 different beers. Make a histogram of the data, pose a statistical question, and describe that distribution. (Source: beer100.com, accessed via StatCrunch. Owner: Webster West)
> Data are available on the number of calories in 12 ounces of beer for 101 different beers. Make a histogram to show the distribution of the numbers of calories, pose a statistical question, and describe the distribution. The first few entries are shown i
> Recently, 115 users of StatCrunch were asked how many text messages they sent in one day. Make a histogram to display the distribution of the numbers of text messages sent, pose a statistical question, and describe the distribution. Some sample data are
> Data are shown for the cost of one year of law school at 30 of the top law schools in the United States in 2013. The numbers are in thousands of dollars. Make a histogram of the costs, pose a statistical question, and describe the distribution. If there
> A StatCrunch survey asked people whether they preferred cats or dogs and how many pets they had. (Those who preferred both cats and dogs and those who preferred another type of pet are not included in these data.) Make two dotplots showing the distributi
> The idea of sending delinquents to “Scared Straight” programs has appeared recently in several media programs (such as Dr. Phil) and on a program called Beyond Scared Straight. So it seems appropriate to look at a rand
> A StatCrunch survey asked people what they thought the maximum income tax rate should be in the United States. Make separate dotplots of the responses from Republicans and Democrats. If possible, put one above the other, using the same horizontal axis. T
> The accompanying table also shows the gestation period (in days) for some animals. The gestation period is the length of pregnancy. Graph the gestation period and describe the distribution. If there are any outliers, identify the animal(s) and give the g
> The following table in Exercise 2.30 shows the average life span for some mammals in years, according to infoplease.com. Graph these average life spans and describe the distribution. What is a typical life span? Identify the three outliers and report the
> The following table shows a random sample of 50 quantitative SAT scores of first-year students admitted at a university. Make an appropriate graph of the distribution of the data, pose a statistical question, and describe the distribution.
> The table shows prices of 50 college textbooks in a community college bookstore, rounded to the nearest dollar. Make an appropriate graph of the distribution of the data, pose a statistical question, and describe the distribution.
> The data show monthly rents for studio and one-bedroom apartments in San Francisco. Write a statistical question appropriate for these data and a brief comparison of the distribution of rents for these two types of housing units. Include appropriate grap
> The weights of Olympic hockey players and soccer players from recent Olympic Games (in pounds) are shown in the following two tables. Make appropriate graphs and use your graphs to write a brief comparison of the distributions of the playersâ€
> Match each description with the correct histogram. 1. Quantitative SAT scores for 1000 students who have been accepted for admission to a private university. 2. Weights of over 500 adults, about half of whom are men and half of whom are women. 3. Ages of
> Match each description with the correct histogram. 1. Heights of students in a large UCLA statistics class that contains about equal numbers of men and women. 2. Numbers of hours of sleep the previous night in the same large statistics class. 3. Numbers
> Match each histogram given with the following descriptions of data. 1. Number of cups of coffee consumed by one person during a day. 2. Maximum speed driven in a car by college students who drive. 3. Number of times last week that a college student had b
> A study carried out by Baturin and colleagues looked at the effects of light on female mice. Fifty mice were randomly assigned to a regimen of 12 hours of light and 12 hours of dark (LD), while another 50 mice were assigned to 24 hours of light (LL). Res
> Match each of the three histograms to the correct situation. 1. Assessed value of a representative collection of houses in a city 2. Number of bedrooms in the houses 3. Height of house (in stories) for houses in a region that allows up to three stories b
> The histograms show the miles per gallon (mpg) for two makes of cars: Acura and BMW. Compare the distributions. Which make has a higher mpg? Which make has more variation in mpg? (Source: Edmonds.com)
> The histograms show the monthly costs for operating two makes of cars: Ford and BMW. Which make typically has higher monthly costs? Which make has more variation in costs? (Source: Edmonds.com)
> The histogram shows the distribution of the numbers of siblings (brothers and sisters) for 2000 adults surveyed in the 2012 General Social Survey. a. Describe the shape of the distribution. b. What is the typical number of siblings, approximately? c. Abo
> In 2012, the General Social Survey (GSS), a national survey conducted nearly every year, reported the number of years of formal education for 2018 people. The following histogram shows the distribution of data. a. Describe and interpret the distribution
> The histograms show triglyceride levels for 87 men and 99 women. Triglycerides are a form of fat found in blood. a. Compare the distributions of triglyceride levels for men and women. (Be sure to compare the shapes, the centers, and the spreads.) b. Trig
> The histograms show the Body Mass Index for 90 females and 89 males according to NHANES. Compare the distributions of BMIs for women and men. Be sure to compare the shapes, the centers, and the amount of variation for the two groups.
> From the histogram shown in Exercise 2.4, what is the typical number of calories for a fast food item in this sample?
> From the histogram in Exercise 2.3, approximately what is the typical pulse rate in this sample?
> The distribution of in-state annual tuition for all colleges and universities in the United States is bimodal. What is one possible reason for this bimodality?
> Researchers wanted to assess whether a theory-based, community health worker–delivered intervention for household smokers will lead to reduced secondhand smoke exposure to children in Chinese families. Smoking parents or caregivers who
> Determine the initial direction of the deflection of charged particles as they enter the magnetic fields, as shown in Figure P19.4. Figure P19.4:
> (a) Find the direction of the force on a proton (a positively charged particle) moving through the magnetic fields in Figure P19.2, as shown. (b) Repeat part (a), assuming the moving particle is an electron. Figure P19.2:
> Find the direction of the magnetic field acting on the positively charged particle moving in the various situations shown in Figure P19.3 if the direction of the magnetic force acting on it is as indicated. Figure P19.3:
> Electrons in Earth’s upper atmosphere have typical speeds near 6.00 x 105 m/s. (a) Calculate the magnitude of Earth’s magnetic field if an electron’s velocity is perpendicular to the magnetic field and its circular path has a radius of 7.00 x 10-2 m. (b)
> A mass spectrometer is used to examine the isotopes of uranium. Ions in the beam emerge from the velocity selector at a speed of 3.00 x 105 m/s and enter a uniform magnetic field of 0.600 T directed perpendicularly to the velocity of the ions. What is th
> Figure P19.14a is a diagram of a device called a velocity selector, in which particles of a specific velocity pass through undeflected while those with greater or lesser velocities are deflected either upwards or downwards. An electric field is directed
> A proton travels with a speed of 5.02 x 106 m/s at an angle of 60° with the direction of a magnetic field of magnitude 0.180 T in the positive x - direction. What are (a) The magnitude of the magnetic force on the proton and (b) The proton’s acceleration
> Sodium ions (Na+) move at 0.851 m/s through a bloodstream in the arm of a person standing near a large magnet. The magnetic field has a strength of 0.254 T and makes an angle of 51.0° with the motion of the sodium ions. The arm contains 100 cm3 of blood
> An oxygen ion (O+) moves in the xy - plane with a speed of 2.50 x 103 m/s. If a constant magnetic field is directed along the z - axis with a magnitude of 2.00 x 10-5 T, find (a) The magnitude of the magnetic force acting on the ion and (b) The magnitude
> A proton moves perpendicular to a uniform magnetic field B( at a speed of 1.00 x 107 m/s and undergoes an acceleration of 2.00 x 1013 m/s2 in the positive x - direction when its velocity is in the positive z - direction. Determine the magnitude and direc
> Two long, parallel conductors separated by 10.0 cm carry currents in the same direction. The first wire carries a current I1 = 5.00 A, and the second carries I2 = 8.00 A. (a) What is the magnitude of the magnetic field created by I1 at the location of I2
> A 1.00 - kg ball having net charge Q = 5.00 μC is thrown out of a window horizontally at a speed v = 20.0 m/s. The window is at a height h = 20.0 m above the ground. A uniform horizontal magnetic field of magnitude B = 0.0100 T is perpendicular to the pl
> A straight wire of mass 10.0 g and length 5.0 cm is suspended from two identical springs that, in turn, form a closed circuit (Fig. P19.74). The springs stretch a distance of 0.50 cm under the weight of the wire. The circuit has a total resistance of 12
> Which way would a compass point if you were at Earth’s north magnetic pole?
> Protons having a kinetic energy of 5.00 MeV are moving in the positive x - direction and enter a magnetic field of 0.0500 T in the z - direction, out of the plane of the page, and extending from x = 0 to x = 1.00 m as in Figure P19.73. (a) Calculate the
> Two long, parallel wires, each with a mass per unit length of 0.040 kg/m, are supported in a horizontal plane by 6.0 - cm - long strings, as shown in Figure P19.72. Each wire carries the same current I, causing the wires to repel each other so that the a
> Three long, parallel conductors carry currents of I = 2.0 A. Figure P19.71 is an end view of the conductors, with each current coming out of the page. Given that a = 1.0 cm, determine the magnitude and direction of the magnetic field at points A, B, and
> A uniform horizontal wire with a linear mass density of 0.50 g/m carries a 2.0 - A current. It is placed in a constant magnetic field with a strength of 4.0 x 10-3 T. The field is horizontal and perpendicular to the wire. As the wire moves upward startin
> Using an electromagnetic flow-meter (Fig. P19.69), a heart surgeon monitors the flow rate of blood through an artery. Electrodes A and B make contact with the outer surface of the blood vessel, which has interior diameter 3.00 mm. (a) For a magnetic fiel
> A 0.200 - kg metal rod carrying a current of 10.0 A glides on two horizontal rails 0.500 m apart. What vertical magnetic field is required to keep the rod moving at a constant speed if the coefficient of kinetic friction between the rod and rails is 0.10
> Two long, straight wires cross each other at right angles, as shown in Figure P19.67. (a) Find the direction and magnitude of the magnetic field at point P, which is in the same plane as the two wires. (b) Find the magnetic field at a point 30.0 cm above
> An electron moves in a circular path perpendicular to a constant magnetic field of magnitude 1.00 mT. The angular momentum of the electron about the center of the circle is 4.00 x 10-25 kg · m2/s. Determine (a) The radius of the circular path and (b) The
> Two coplanar and concentric circular loops of wire carry currents of I1 = 5.00 A and I2 = 3.00 A in opposite directions as in Figure P19.65. (a) If r1 = 12.0 cm and r2 = 9.00 cm, what are the magnitude and (b) The direction of the net magnetic field at t
> Figure P19.64 is a setup that can be used to measure magnetic fields. A rectangular coil of wire contains N turns and has a width w. The coil is attached to one arm of a balance and is suspended between the poles of a magnet. The field is uniform and per
> Consider an electron near the Earth’s equator. In which direction does it tend to deflect if its velocity is (a) Directed downward? (b) Directed northward? (c) Directed westward? (d) Directed southeastward?
> An electron is moving at a speed of 1.0 x 104 m/s in a circular path of radius 2.0 cm inside a solenoid. The magnetic field of the solenoid is perpendicular to the plane of the electron’s path. Find (a) The strength of the magnetic field inside the solen
> Certain experiments must be performed in the absence of any magnetic fields. Suppose such an experiment is located at the center of a large solenoid oriented so that a current of I = 1.00 A produces a magnetic field that exactly cancels Earth’s 3.50 x 10
> It is desired to construct a solenoid that will have a resistance of 5.00 Ω (at 20°C) and produce a magnetic field of 4.00 x 10-2 T at its center when it carries a current of 4.00 A. The solenoid is to be constructed from copper wire having a diameter of
> A certain superconducting magnet in the form of a solenoid of length 0.50 m can generate a magnetic field of 9.0 T in its core when its coils carry a current of 75 A. The windings, made of a niobium–titanium alloy, must be cooled to 4.2 K. Find the numbe
> A long solenoid that has 1.00 x 103 turns uniformly distributed over a length of 0.400 m produces a magnetic field of magnitude 1.00 x 10-4 T at its center. What current is required in the windings for that to occur?
> In Figure P19.58 the current in the long, straight wire is I1 = 5.00 A, and the wire lies in the plane of the rectangular loop, which carries 10.0 A. The dimensions shown are c = 0.100 m, a = 0.150 m, and â„“ = 0.450 m. Find the magnitude
> A wire with a weight per unit length of 0.080 N/m is suspended directly above a second wire. The top wire carries a current of 30.0 A, and the bottom wire carries a current of 60.0 A. Find the distance of separation between the wires so that the top wire
> Two parallel wires separated by 4.0 cm repel each other with a force per unit length of 2.0 = 10-4 N/m. The current in one wire is 5.0 A. (a) Find the current in the other wire. (b) Are the currents in the same direction or in opposite directions? (c) Wh
> Two long, parallel wires separated by 2.50 cm carry currents in opposite directions. The current in one wire is 1.25 A, and the current in the other is 3.50 A. (a) Find the magnitude of the force per unit length that one wire exerts on the other. (b) Is
> Two long, parallel wires separated by a distance 2d carry equal currents in the same direction. An end view of the two wires is shown in Figure P19.54, where the currents are out of the page. (a) What is the direction of the magnetic field at P on the x
> The north - pole end of a bar magnet is held near a stationary positively charged piece of plastic. Is the plastic (a) Attracted, (b) Repelled, or (c) Unaffected by the magnet?
> The magnetic field 40.0 cm away from a long, straight wire carrying current 2.00 A is 1.00 μT. (a) At what distance is it 0.100 μT? (b) At one instant, the two conductors in a long household extension cord carry equal 2.00 - A currents in opposite direct
> A long, straight wire lies on a horizontal table in the xy - plane and carries a current of 1.20 μA in the positive x - direction along the x - axis. A proton is traveling in the negative x - direction at speed 2.30 x 104 m/s a distance d above the wire
> A wire carries a 7.00 - A current along the x - axis, and another wire carries a 6.00 - A current along the y - axis, as shown in Figure P19.51. What is the magnetic field at point P, located at x = 4.00 m, y = 3.00 m? Figure P19.51:
> Two long, parallel wires carry currents of I1 = 3.00 A and I2 = 5.00 A in the direction indicated in Figure P19.50. (a) Find the magnitude and direction of the magnetic field at a point midway between the wires (d = 20.0 cm). (b) Find the magnitude and d
> Four long, parallel conductors carry equal currents of I = 5.00 A. Figure P19.49 is an end view of the conductors. The direction of the current is into the page at points A and B (indicated by the crosses) and out of the page at C and D (indicated by the
> The two wires shown in Figure P19.48 are separated by d = 10.0 cm and carry currents of I = 5.00 A in opposite directions. Find the magnitude and direction of the net magnetic field (a) At a point midway between the wires; (b) At point P1, 10.0 cm to the
> A cardiac pacemaker can be affected by a static magnetic field as small as 1.7 mT. How close can a pacemaker wearer come to a long, straight wire carrying 20 A?
> In 1962 measurements of the magnetic field of a large tornado were made at the Geophysical Observatory in Tulsa, Oklahoma. If the magnitude of the tornado’s field was B = 1.50 x 10-8 T pointing north when the tornado was 9.00 km east of the observatory,
> Neurons in our bodies carry weak currents that produce detectable magnetic fields. A technique called magne-toencephalography, or MEG, is used to study electrical activity in the brain using this concept. This technique is capable of detecting magnetic f
> A long, straight wire going through the origin is carrying a current of 3.00 A in the positive z - direction (Fig. P19.44). At a point a distance r = 1.20 m from the origin on the positive x - axis, find the (a) Magnitude and (b) Direction of the magneti
> A charged particle moves in a straight line through a region of space. Which of the following answers must be true? (Assume any other fields are negligible.) The magnetic field (a) Has a magnitude of zero (b) Has a zero component perpendicular to the par
> A lightning bolt may carry a current of 1.00 x 104 A for a short time. What is the resulting magnetic field 1.00 x 102 m from the bolt? Suppose the bolt extends far above and below the point of observation.
> A rectangular loop has dimensions 0.500 m by 0.300 m. The loop is hinged along the x - axis and lies in the xy - plane (Fig. P19.42). A uniform magnetic field of 1.50 T is directed at an angle of 40.0° with respect to the positive y - axis and
> A long piece of wire with a mass of 0.100 kg and a total length of 4.00 m is used to make a square coil with a side of 0.100 m. The coil is hinged along a horizontal side, carries a 3.40 - A current, and is placed in a vertical magnetic field with a magn
