Cumulative Exam — Cumulative exam Answers

The side-by-side dotplot below displays the arm spans, in centimeters, for two classes.

A student is preparing to take a standardized exam. She was told that she needs to get plenty of sleep the night before the exam. She is interested in the relationship between the number of hours of sleep a student gets before the exam and the score earned on the exam. She collects information from 10 other students who have already taken the exam as shown in the table.She fits a least-squares regression line to the data and determines the equation of the line is ŷ =26 – 0.18x, where ŷ is the score earned on the exam and x is the number of hours of sleep the night before the exam. The residual plot is given.

Many delivery trucks feature a "How Am I Driving?” sticker on the rear bumper, along with a phone number. This sticker allows drivers to report erratic driving by the truck driver or offer a compliment if they like. A dispatcher at the trucking station accepts calls and records information from those who call the phone number. The dispatcher reports that in the past month, 218 calls were received. Of those calls, 178 reported negative driving behaviors by the truck drivers. How might this data-collection method produce bias in obtaining an estimate of all drivers who are satisfied with the company’s truck drivers?

The weight (in pounds) and height (in inches) for a child were measured every few months over a two-year period. The results are given in the table.

A new cream was developed to reduce the irritation caused by poison ivy. To test the effectiveness, researchers placed an ad online asking for volunteers to participate in the study, and 100 subjects replied. They are informed that one group of 50 will receive a new cream and the remaining group of 50 will receive a cream with no active ingredient. The subjects are numbered 1–100 and these numbers are put into a random number generator. The first 50 unique numbers will represent the subjects that will receive the new cream and the remaining 50 subjects will receive the inactive cream. All subjects are exposed to poison ivy and given their cream. They are asked to return in three days and report their level of irritation. The average scores for each cream are compared.

The dotplot below displays the difference in scores for 18 games between a high school soccer team and its opponent.

Response time is an important statistic for measuring the effectiveness of a fire department, and is measured as the difference between the time a fire house receives a call and the time the first piece of fire equipment leaves the station. The response times for fire departments in a large city are found to have an approximately Normal distribution, with a mean of 4.5 minutes and a standard deviation of 1.2 minutes. What percentage of fire station response times are between 4 and 6 minutes?Find the z-table here.

A statistics student is studying if there is a relationship between the price of a used car and the number of miles it has been driven. She collects data for 20 cars of the same model with different mileage, and determines each car’s price using a used car website. The analysis is given in the computer output.PredictorCoefSE Coeft-ratiopConstant24157.22164.12.9650.046Mileage-0.1810.0245.3770.000S = 3860.7R-Sq = 68.0%R-Sq(Adj) = 67.5%

The graph shows the distribution of times (in hours) that teenagers spend playing video games per week. The distribution is approximately Normal, with a mean of 14 hours and a standard deviation of 4 hours.

Elementary school students were given a geometry assignment. They were to measure the area of several rectangles and to measure the diagonal of the rectangle as shown in the table.

A farmer sows 100 seeds of a new type of corn and wants to quickly determine the yield, or total number of ears of corn, for the crop when it has matured. He decides to take a simple random sample of 10 corn plants. He labels the 100 plants 00–99. Refer to the given line from a random number table. Which numbers represent the sample of 10 corn plants?58160 09695 38399 40400 32662 46254

The president of the student council wants to survey the student population about parking. She decides to take a random sample of 100 of the 1,020 students at the school. She gets an alphabetical list of the students, and numbers them from 0001 to 1020. Then, using a random number table, and starting at a random line, she selects 100 unique numbers between 0001 and 1020. Is this a simple random sample?

Cell phone production engineers have noticed that among a group of 138 customers aged 14-23 who send more text messages tend to use a higher percentage of their phone’s memory.

The weights of packs of chewing gum for a certain brand have a mean of 47.1 grams and a standard deviation 2.4 grams. The weight of a randomly selected pack of gum has a z-score of 3.11. Which of the following statements is the best interpretation of the z-score?

The graph shows the distribution of the lengths (in seconds) of videos on a popular video-streaming site. The distribution is approximately Normal, with a mean of 264 seconds and a standard deviation of 75 seconds.

A tire company wants to determine if tires made with a new type of tread will last longer than tires made with the original type of tread. The company has access to 24 different vehicles. Each vehicle will receive four tires with the new tread and four with the original tread. The position, front or back, will be randomly determined for a pair of each type of tread. For example, a vehicle will have the new type of tread on the front tires and the original tread on the back tires. After six months, the pairs of unused tires will be used with the position switched on the car. The vehicles will be driven for six more months. At the end of one year, the depths of the remaining tread will be measured for each tire and the average differences between the new and original tread types will be determined. The average differences will then be used to determine if the new tread does last longer.

Fuel efficiency, measured in miles per gallon, is a feature often considered by shoppers looking for a new car. The scatterplot shows the vehicle weight of 15 car models in pounds, plotted against their highway fuel efficiency.

Fuel efficiency, measured in miles per gallon, is a measure often considered by shoppers looking for a new car. The scatterplot shows the vehicle weight of 15 car models in pounds, plotted against their highway fuel efficiency.

A statistics teacher has 4 periods of introductory statistics. She wants to get students’ opinions on a new homework policy. To get a sample, the teacher groups the students by their class performance (A students, B students, etc.). Then she randomly selects 3 students from each class performance group to survey. Which sampling method was used?