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# Confidence Interval

### A marketing firm wants to estimate an average amount spent at the hospital pharmacy

(TCO 7) A marketing firm wants to estimate the average amount spent by patients at the hospital pharmacy. For a sample of 100 randomly selected patients, the mean amount spent was \$65.30 and the standard deviation \$8.15. (a) Find a 99% confidence interval for the mean amount spent by patients at the pharmacy. Show your calcu

### A drug manufacturer wants to estimate the mean heart rate for certain heart conditions

(TCO 7) A drug manufacturer wants to estimate the mean heart rate for patients with a certain heart condition. Because the condition is rare, the manufacturer can only find 18 people with the condition currently untreated. From this small sample, the mean heart rate is 93 beats per minute with a standard deviation of 6. (a)

### Statistics: Should Tesla Motors buy axles from Crhis Cross Manufacturing

Tesla Motors needs to buy axles for their new car. They are considering using Chris Cross Manufacturing as a vendor. Tesla's requirement is that 95% of the axles are 100 cm ± 2 cm. The following data is MegaStat output from a test run from Chris Cross Manufacturing. Should Tesla select them as a vendor? Explain your answer.

### Confidence Interval: Mean Salary of Google Managers

A random sample a 16 Google managers yield the following information on annual salaries. The sample mean is \$69,000, with a sample standard deviation of \$4,000. What is the mean salary of all Google managers? What is the 95% confidence interval for the population mean? Confidence interval - mean 95%

### True mean

A nursing school wants to estimate the true mean annual income of its alumni. It randomly samples 120 of its alumni. The mean annual income was \$58,700 with a standard deviation of \$1,500. Find a 95% confidence interval for the true mean annual income of the nursing school alumni. Write a statement about the confidence level a

### Confidence Interval and Sample Size

1. A consumer group would like to estimate the average amount of P G and E bill for the month of March for single family homes in the San Francisco Bay area. Based on studies conducted in other similar climate cities, the standard deviation is assumed to be \$25. The group would like to estimate the average March bill to be withi

### Interpreting a confidence interval

1. If the 95% confidence interval for the average age of a learner at Capella is 27.8 yrs. < MEAN < 32.6 yrs., what would your reaction be to the brochure that states the average age of a Capella learner is less than 25? 2. Studies have shown that 50% of people who have died have done so within 3 months of their birthday.

### Statistics: Problems and Solutions

1. A sample of 35 golfers showed that their average score on a particular golf course was 80 with a standard deviation of 6. Answer each of the following (show all work): (A) Find the 95% confidence interval of the mean score for all 35 golfers. (B) Find the 95% confidence interval of the mean score for all golfers if this

### Estimations, Confidence intervals, Sample Size

Why are estimations and confidence intervals important? Do confidence intervals and estimation play a role in the selection of sample size? Please explain your answer.

### Statistics: Problems and Solutions

22. List the reasons for sampling. Give an example of each reason for sampling. 34. Information from the American Institute of Insurance indicates the mean amount of life insurance per household in the United States is \$110,000. This distribution follows the normal distribution with a standard deviation of \$40,000. a. If w

### Business Statistics: Relationship between Confidence Intervals & Hypothesis Testing

What is the relationship between confidence intervals and hypothesis testing? How are they the same? How are they different?

### Interpret confidence intervals for average daily exercise times

Please show all work. Calculate and interpret the following confidence intervals 1) 95% CI for the average daily exercise time of males 2) 99% CI for the average daily exercise time of females Data (in minutes): males (15): 60 40 50 90 50 60 10 10 35 70 43 25 15 25 30 females (15): 45 55 60 60 4

### Finding Confidence Interval and Sample Size Example Questions

1. The Internal Revenue Service is studying contributions to charity. The mean calculated from a random sample of 36 returns is \$150. Assume that the population standard deviation is known and equal to \$20. Construct a 98 percent confidence interval for the population mean. 2. A large bank believes that one-third of its ch

### Statistics: confidence interval, Margin of error, Sample mean, Population variance

1. A researcher wishes to estimate with 99% Confidence, the proportion of adults who have high-speed internet access. Her estimate must be accurate within 5% of the true Proportion. (a) Find the minimum sample needed, using a prior study that found that 54% of the respondents said they have high-speed internet access. (b) No p

### Statistics: mean repair cost for washing machine; 10 bottles of cough syrup

1. YOU WORK FOR A CONSUMER ADVOCATE AGENCY AND WANT TO FIND THE MEAN REPAIR COST OF A WASHING MACHINE. AS PART OF YOUR STUDY, YOU RANDOMLY SELECT 55 REPAIR COSTS AND FIND THE MEAN TO BE \$131.00. THE SAMPLE STANDARD DEVIATION IS \$17.00. COMPLETE PARTS (a) and (b). (a) Construct a 905 confidence interval for the population me

### Confidence interval: Take-out dinner, Grand Strand Medical, real estate, TV news

27. A recent study focused on the number of times men and women who live alone buy take-out dinner in a month. The information is summarized below. At the .01 significance level, is there a difference in the mean number of times men and women order take-out dinners in a month? What is the p-value? Statistic Men Women S

### Small sample confidence interval for a population mean

Your quality control department has just analyzed the contents of 20 randomly selected barrels of materials to be used in manufacturing plastic garden equipment. The results found an average of 41.93 gallons of usable material per barrel, with a standard error of 0.040 gallon per barrel. Find the two sided 95% confidence interva

### Effect on costs for reduced length of patient hospital stay

Your hospital is negotiating with medical insurance providers, who would like to reduce the amount they pay as reimbursement for hospital stays. For a particular procedure, they would like to reduce payment by \$300 and have patients go home one day earlier. To see what effect this would have one hospital costs, a random samp

### Confidence intervals, null hypothesis for population mean weight loss

Attached is the data needed. 1. Test the null hypothesis that the population mean weight loss is zero versus the alternative hypothesis that the mean weight loss is greater than zero. use .05 and assume the population of weight loss is normally distributed. Also compute the p value. 2. What values of the sample mean we

### Confidence Interval for Population Proportion & Margin Error

A sample of 800 adults was chosen to determine the proportion of adults who favor legalized gambling. 1. What's the margin of error for the study? 2. If the sample proportion is .54, determine a 95% confidence interval for the population proportion. 3. If it turns out 53% of adults favor legalized gambling, what's th

### Estimation, ANOVA: TV watching by students, motor skills of children, T-test

1. Explain why it would not be reasonable to use estimation after a hypothesis test for which the decision was "fail to reject Ho. 2. An elementary school principal would like to know how many hours the students spend watching TV each day. A sample of n = 25 children is selected, and a survey is sent to each child's parents.

### Statistics: 11 multiple choice for confidence interval, sample mean, probability, sample

Q1. In evaluating the effectiveness of the state rehabilitation program, a survey of 49 prisoners (from several thousand prisoners in prison) found that 35 percent were repeat offenders. What is the 90 percent confidence interval for the proportion of repeat offenders amount the prisoners? A. 0.216, 0.484 B. 0.516, 0.784 C

### Statistics Chapter 12: Estimation with the t Statistic for fine motor skills of children

A developmental psychologist would like to determine how much fine motor skill improves for children from age 3 to age 4. A random sample of n = 15 3 year old children and a second sample of n = 15 4 year olds are obtained. Each child is given a manual dexterity test that measure fine motor skills. The average score for the olde

### Statistics for the Behavioral Sciences: T Statistics for motor skill of children

A developmental psychologist would like to determine how much fine motor skill improves for children from age 3 to age 4. A random sample of n = 15 3 year old children and a second sample of n = 15 4 year olds are obtained. Each child is given a manual dexterity test that measure fine motor skills. The average score for the olde

### Standard Deviation and Confidence Interval: Example Problem

From the attached document, I have a table and histogram of men's vs. women's wages. I am supposed to calculate the standard deviation and confidence interval. Please explain the steps necessary to obtain these figures.

### Hypothesis Testing & Confidence Interval : Solution set

See the attached is an excel spreadsheet with the necessary information to complete the problem. I am doing a study on alcohol consumption between males and females (two independent samples continuous outcome)this is my hypothesis: H1: = Men are able to consume more alcoholic beverages than women Ho:= Men and

### Population Mean and Confidence Interval

1. A state meat inspector in Iowa has been given the assignment of estimating the mean net weight of packages of ground chuck labeled "3 pounds." Of course, he realizes that the weights cannot be precisely 3 pounds. A sample of 36 packages reveals the mean weight to be 3.01 pounds, with a standard deviation of 0.03 pounds. a.

### Large Coverage Errors for Interviewers Bias

1) A poll is planned to determine what proportion of all students favor an increase in fees to support a new track and field stadium. A questionnaire will be published and the first 1000 completed questionnaires will be analyzed. Which of the following errors will be associated with the sample? A. Only non-sampling errors

### Normal probability

I have tried to answer these questions but I need a little help 1.(use the Normal Probability file) In a recent year, about two-thirds of U.S. households purchased ground coffee. Consider the annual ground coffee expenditures for households purchasing ground coffee, assuming that these expenditures are approximately distribut

### Find a 98% confidence interval for the true mean heart rate of all people with the untreated condition. Interpret this confidence interval and write a sentence that explains it.

A drug manufacturer wants to estimate the mean heart rate for patients with a certain heart condition. Because the condition is rare, the manufacturer can only find 29 people with the condition currently untreated. From this small sample, the mean heart rate is 90 beats per minute with a standard deviation of 5. (a) Find a 98