1. A recent survey of local cell phone retailers showed that of all cell phones sold last month, 64% had a camera, 28% had a music player and 22% had both. Which of the following statements about cell phones sold last month is true?
Having a camera and having a music player are mutually exclusive events.
The intersection of having a camera and having a music player is zero.
Having a camera and having a music player are independent events.
Having a camera and having a music player are disjoint events.
Having a camera and having a music player are not mutually exclusive events.
1. The number of male babies in a sample of 10 randomly chosen babies is a:
continuous random variable
Poisson random variable
binary random variable
binomial random variable
1. Thirty work orders are selected from a filing cabinet containing 500 work order folders by choosing every 15th folder. Which sampling method is this?
Simple random sample
1. A sample of 250 people resulted in a confidence interval estimate for the proportion of people who believe that the federal government’s proposed tax increase is justified is between 0.14 and 0.20. Based on this information, what was the confidence level used in this estimation?
Approximately 79 percent
Can’t be determined without knowing σ (sigma).
1. A 99% confidence interval estimate can be interpreted to mean that
if all possible samples are taken and confidence interval estimates are developed, 99% of them would include the true population mean somewhere within their interval.
we have 99% confidence that we have selected a sample whose interval does include the population mean.
both of the above.
none of the above.
1. At the U.S. Open Tennis Championship a statistician keeps track of every serve that a player hits during the tournament. The statistician reported that the mean serve speed of a particular player was 105 miles per hour (mph) and the standard deviation of the serve speeds was 9 mph. If nothing is known about the shape of the distribution, give an interval that will contain the speeds of at least eight-ninths of the player’s serves.
87 mph to 123 mph
132 mph to 159 mph
69 mph to 141 mph
78 mph to 132 mph
1. Chebychev’s Theorem:
applies to all samples
applies only to samples from a normal population
gives a narrower range of predictions than the Empirical Rule
is based on Sturges’ Rule for data classification
1. A major department store chain is interested in estimating the average amount its credit card customers spent on their first visit to the chain’s new store in the mall. Fifteen credit card accounts were randomly sampled and analyzed with the following results: X (i.e. Xbar = $50.50) and s2(i.e. s squared = 400). Assuming the distribution of the amount spent on their first visit is approximately normal, what is the shape of the sampling distribution of the sample mean that will be used to create the desired confidence interval for μ (mew)?
Approximately normal with a mean of $50.50
A standard normal distribution
A t distribution with 15 degrees of freedom
A t distribution with 14 degrees of freedom
1. As part of an economics class project, students were asked to randomly select 500 New York Stock Exchange (NYSE) stocks from the Wall Street Journal. As part of the project, students were asked to summarize the current prices (also referred to as the closing price of the stock for a particular trading date) of the collected stocks using graphical and numerical techniques. Identify the sample of interest for this study.
the current price (or closing price) of a NYSE stock
the entire set of stocks that are traded on the NYSE
a single stock traded on the NYSE
the 500 NYSE stocks that current prices were collected from
1. A standardized test has a mean score of 500 points with a standard deviation of 100 points. Five students’ scores are shown below.
Which of the students have scores within two standard deviations of the mean?
Adam, Beth, Ella
Adam, Beth, Carlos, Ella
1. Suppose a sample of n = 50 items is drawn from a population of manufactured products and the weight, X, of each item is recorded. Prior experience has shown that the weight has a probability distribution with μ = 6 ounces (mew = 6 ounces) and σ = 2.5 ounces (sigma = 2.5 ounces). Which of the following is true about the sampling distribution of the sample mean if a sample of size 15 is selected?
The mean of the sampling distribution is 6 ounces.
The standard deviation of the sampling distribution is 2.5 ounces.
The shape of the sample distribution is approximately normal.
All of the above are correct.
1. A probability distribution is an equation that
associates a particular probability of occurrence with each outcome in the sample space.
measures outcomes and assigns values of X to the simple events.
assigns a value to the variability in the sample space.
assigns a value to the center of the sample space.
1. A survey was conducted to determine how people feel about the quality of programming available on television. Respondents were asked to rate the overall quality from 0 (no quality at all) to 100 (extremely good quality). The stem-and-leaf display of the data is shown below.
What percentage of the respondents rated overall television quality as very good (regarded as ratings of 80 and above)?
1. A statistics professor wanted to test whether the grades on a statistics test were the same for upper and lower classmen. The professor took a random sample of size 10 from each, conducted a test and found out that the variances were equal. For this situation, the professor should use a t test with independent samples.
1. At a computer manufacturing company, the actual size of computer chips is normally distributed with a mean of 1 centimeter and a standard deviation of 0.1 centimeter. A random sample of 12 computer chips is taken. What is the standard error for the sample mean?
1. Which display is most likely to reveal association between X and Y?
1. During its grand opening week, Stickler’s bicycle shop offers a “wheel of discount savings.” After customers select the items they wish to purchase, they spin the wheel to determine the discount they will receive. The wheel is divided into 12 slices. Six slices are red and award a 10% discount, three slices are white and award a 20% discount, and two slices are blue and award a 40% discount. The remaining slice is gold and awards a 100% discount! The probability that a customer gets at least a 40% discount is
1. Which model would you use to describe the probability that a call-center operator will make the first sale on the third call, assuming a constant probability of making a sale?
1. The amount spent on textbooks for the fall term was recorded for a sample of five university students – $400, $350, $600, $525, and $450. Calculate the value of the sample standard deviation for the data.
1. Suppose the ages of students in Statistics 101 follow a skewed-right distribution with a mean of 23 years and a standard deviation of 3 years. If we randomly sampled 100 students, which of the following statements about the sampling distribution of the sample mean age is incorrect?
The mean of the sampling distribution is equal to 23 years.
The standard deviation of the sampling distribution is equal to 3 years.
The shape of the sampling distribution is approximately normal.
The standard error of the sampling distribution is equal to 0.3 years.
1. A die is rolled. If it rolls to a 1, 2, or 3 you win $2. If it rolls to a 4, 5, or 6 you lose $1. Find the expected winnings.
1. What type of probability distribution will the consulting firm most likely employ to analyze the insurance claims in the following problem? An insurance company has called a consulting firm to determine if the company has an unusually high number of false insurance claims. It is known that the industry proportion for false claims is 3%. The consulting firm has decided to randomly and independently sample 100 of the company’s insurance claims. They believe the number of these 100 that are false will yield the information the company desires.
none of the above.
1. If we are testing for the difference between the means of 2 independent populations presuming equal variances with samples of n1 = 20 (i.e. n1 = 20) and n2 = 20 (i.e. n2 = 20), the number of degrees of freedom is equal to
1. The option to buy extended warranties is commonplace with most electronics purchases. But does the type of purchase affect a consumer’s willingness to pay extra for an extended warranty? Data for 420 consumers who purchased digital cameras and laptop computers from a leading electronics retailer are summarized in the table. The probability that a consumer does not purchase an extended warranty is
1. The amount of television viewed by today’s youth is of primary concern to Parents Against Watching Television (PAWT). 300 parents of elementary school-aged children were asked to estimate the number of hours per week that their child watches television. The mean and the standard deviation for their responses were 17 and 3, respectively. PAWT constructed a stem-and-leaf display for the data that showed that the distribution of times was a symmetric, mound-shaped distribution. Give an interval where you believe approximately 95% of the television viewing times fell in the distribution.
between 8 and 26 hours per week
less than 14 and more than 20 hours per week
between 11 and 23 hours per week
less than 23
1. Consider the following data: 6, 7, 17, 51, 3, 17, 23, and 69. The range and the median are:
69 and 17.5
66 and 17.5
66 and 17
69 and 17
1. For quality control purposes, a company that manufactures copper sheets routinely takes samples from its production process. Since its product is often used for decorative purposes, one inspection check involves counting the number of imperfections or flaws on sheets that measure 36 sq. ft. Suppose the average number of imperfections per sheet of this size is 3. What is the probability that a sheet of this size has 2 imperfections?
1. The standard error of the mean
is never larger than the standard deviation of the population.
decreases as the sample size increases.
measures the variability of the mean from sample to sample.
all of the above.
1. Suppose that incoming calls per hour to a customer service center of a small credit union are uniformly distributed between 0 and 6 calls. The probability that fewer than 3 calls are received per hour is
1. If the outcomes of a random variable follow a Poisson distribution, then their
mean equals the standard deviation.
median equals the standard deviation.
mean equals the variance.
median equals the variance.
1. Parking at a university has become a problem. University administrators are interested in determining the average time it takes a student to find a parking spot. An administrator inconspicuously followed 270 students and recorded how long it took each of them to find a parking spot. Identify the variable of interest to the university administration.
number of students who cannot find a spot
students who drive cars on campus
number of empty parking spots
time to find a parking spot
1. What number is missing from the table?
1. The t test for the difference between the means of 2 independent populations assumes that the respective
sample sizes are equal.
sample variances are equal.
populations are approximately normal.
all of the above.
1. Temperature in degrees Fahrenheit is an example of a(n) __________ variable.
1. The amount of television viewed by today’s youth is of primary concern to Parents Against Watching Television (PAWT). 330 parents of elementary school-aged children were asked to estimate the number of hours per week that their child watches television. Identify how the data were collected in this study.
from a published source
from a designed experiment
from a survey