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|