QUESTION 1
Refer to the following breakdown of responses to a survey of room cleanliness in a hotel.
What is the class interval for the following frequency table?
If there is a class interval, give the value, if no class interval, then the answer is 0.
5 points
QUESTION 2
The following frequency distribution shows the distribution of delivery times (in days) for swimstuff.com customer orders during the last month.
What is the relative frequency for orders delivered in three days or more?
5 points
QUESTION 3
The mean monthly income of a group of college students is $500; the standard deviation is $50. And the mean monthly income is normally distributed. Approximately, what percent of the incomes will lie between $400 and $600?
5 points
QUESTION 4
In flipping a fair coin, what is the probability of either heads or tails on one toss?
5 points
QUESTION 5
Airlines monitor the causes of flights arriving late. A total of 75% of flights are late because of weather, while 35% of flights are late because of ground operations. A full 10% of flights are late because of weather and ground operations. What is the joint probability that a flight arrives late because of weather and ground operations?
5 points
QUESTION 6
Affirmative action commitments by many organizations have led to an increase in the number of women in executive positions. Satellite Office Systems has vacancies for two executives that it will fill from among four women and six men.
What is the probability that exactly one woman is selected?
5 points
QUESTION 7
Elly’s
Elly’s Hotdog Emporium is famous for its chilidogs. Elly’s latest sales indicate that 30% of the customers order their chilidogs with hot peppers. Suppose 15 customers are selected at random. What is the probability that exactly 10 customers will ask for hot peppers?
5 points
QUESTION 8
From past history, the scores on a statistics test are normally distributed with a mean score of 70 and a standard deviation of 5. To earn a “C” on the test, a student must be in the top 25% of the class. A student would need to score at least ______ to receive a “C” grade.
5 points
QUESTION 9
A university has 1,000 computers available for students to use. Each computer has a 250-gigabyte hard drive. The university wants to estimate the space occupied on the hard drives. A random sample of 100 computers showed a mean of 115 gigabytes used with a standard deviation of 20 gigabytes. What is the probability that a sample mean is greater than 120 gigabytes?
5 points
QUESTION 10
A local grocery store wants to estimate the mean daily number of gallons of milk sold to customers. Assume the number of gallons sold follows the normal distribution, with a population standard deviation of 5.10 gallons. A random sample of 60 days shows that the mean daily number of gallons sold is 10.00. Compute a 99% confidence interval for the population mean.
5 points
QUESTION 11
Records on a fleet of trucks reveal that the average life of a set of spark plugs is normally distributed with a mean of 22,100 miles. The fleet owner purchased 18 sets and found that the sample average life was 23,400 miles; the sample standard deviation was 1,412 miles. To determine if the spark plugs average 22,100 miles, what is the critical value for the test using a 0.05 level of significance?
5 points
QUESTION 12
A manufacturer wants to increase the shelf life of a line of cake mixes. Past records indicate that the average shelf life of the mix is 216 days. After a revised mix has been developed, a sample of nine boxes of cake mix had a mean of 217.222 days and a standard deviation of 1.2019 days. At the 0.025 significance level, decide if the sample data support the claim that shelf life has increased. State your decision in terms of the null hypothesis.
5 points
QUESTION 13
To test the hypothesis that two population variances are equal, a random sample of size 13 was selected from the first population, and a random sample of size 21 was selected from the second population. Given that the sample standard deviation from the first population is larger than the sample standard deviation from the second population, what is the F critical value using 0.01 as the significance level?
5 points
QUESTION 14
Given the data below, compute r using the z-score method.
X Y
1 2
2 10
3 7
5 points
QUESTION 15
A random sample of 400 families who planned to buy a vacation residence revealed that 228 families want to buy a condominium in Florida. At the 0.01 significance level, test the statement that 55% of those families who plan to purchase a vacation residence in Florida want a condominium. To decide if the sample data support the 55%, state your decision in terms of the null hypothesis. Use a 0.01 level of significance.
5 points
QUESTION 16
For a given set of 12 ranked data values, the sum of the squared differences is 63.18. What is Spearman’s coefficient of rank correlation for the data?
5 points
QUESTION 17
Twenty economists were sampled and asked to predict if the national economy would improve during the next 12 months. Eleven of the economists predicted an increase, two economists predicted no change, and seven economists predicted a decrease in the economy. Conduct a hypothesis test at the 0.10 significance level to determine if the majority of economists predict an increase.
The null hypothesis is:
5 points
QUESTION 18
Suppose the following are the ages of a group of individuals enrolled in a study looking at the relationship between sleep apnea and Alzheimer’s disease.
67, 87, 92, 86, 83, 85, 72, 65, 68, 73, 98, 78, 61, 90, 85, 84, 83, 72
A) Create a stem-and-leaf plot for the distribution of ages in this study.
B) Interpret the stem-and-leaf plot with respect to the spread of the distribution.
5 points
QUESTION 19
Suppose a researcher is interested in determining if there is a relationship between low birth weight and pediatric pneumonia. In order to test this relationship, the researcher will use a σ=746 grams and a margin of error plus or minus 646 grams. How many newborns will the researcher need to sample in order to be 95% confident?
5 points
QUESTION 20
In your own words, explain the difference between classification, clustering and association algorithms, give an example of application using each algorithm.