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# Confidence Interval

### Statistics: Difference in mean total cholesterol levels between treatments

8. The following data were collected in a clinical trial to compare a new drug to a placebo for its effectiveness in lowering total serum cholesterol. Generate a 95% confidence interval for the difference in mean total cholesterol levels between treatments. New Drug (n=75), Mean (SD) Total Serum Cholesterol = 185.0

### Need help with this

5. A study is run comparing HDL cholesterol levels between men who exercise regularly and those who do not. The data are shown below. Regular Exercise = Yes, N = 35,Mean = 48.5, Std Dev = 12.5 Regular Exercise = No, N =120, Mean = 56.9 ,Std Dev = 11.9 Generate a 95% confidence interval for the differenc

### Confidence Interval & Sample size: Body Mass Index

1. The following are body mass index (BMI) scores measured in 12 patients who are free of diabetes and participating in a study of risk factors for obesity. Body mass index is measured as the ratio of weight in kilograms to height in meters squared. Generate a 95% confidence interval estimate of the true BMI. 25, 27, 31 ,33

### Random sample of 40 members of YMCA of South Jersey

See Attachment. Marty Rowatti recently assumed the position of director of the YMCA of South Jersey. He would like some current data on how long current members of the YMCA have been members. To investigate, suppose he selects a random sample of 40 current members. The mean length of membership of those in

### Confidence Interval for population of 50 executives who were laid off

Each response must include your calculations. A recent survey of 50 executives who were laid off from their previous position revealed it took a mean of 26 weeks for them to find another position. The standard deviation of the sample was 6.2 weeks. Complete the following: (show your work to the right)

### Construct the 99 percent confidence interval

See Attachment. Construct the 99 percent confidence interval for the population proportion. Furniture Land South surveyed 600 consumers and found that 414 were enthusiastic about a new home décor they plan to show in their store in High Point, North Carolina.

### Margin of error for sample of IRS tax returns for itemized deductions

Please show all work. 1) The Internal Revenue Service plans to examine an SRS of individual federal income tax returns from each state. One variable of interest is the proportion of returns claiming itemized deductions. The total number of tax returns in a state varies from more than 15 million in California to fewer than 250

### Statistics: Test life style changes considered effective for reducing cholesterol levels

Please explain all work. In order for a lifestyle change to be considered effective, the target is to have the average cholesterol of this group be below 200. After 6 months of exercising more and eating better, an SRS of 51 patients at risk for heart disease had an average cholesterol of x = 192, with a standard deviation s

### Normal Probability & Margin of Error

1. A population has a mean of 80 and a standard deviation of 7. A sample of 49 observations will be taken. The probability that the sample mean will be larger than 82 is? 2. With a .95 probability, the sample mean will provide a margin of error of?

### Statistics: Confidence interval for population mean; estimate value of the mean

Questions A sample of 81 observations is taken from a normal population with a standard deviation of 5. The sample mean is 40. Determine the 95% confidence interval for the population mean. ____________ Dr. Patton is a professor of English. Recently she counted the number of misspelled words in a group of student essays

### Hypothesis testing and confidence interval question

Kids Adults Totals Green Bikes 900 600 Red Bikes 600 400 Totals 5 Steps of Hypothesis Testing and interpret your decision. Construct a 90% confidence interval for the proportion of adults that bought green bikes. SHOW IN DETAIL HOW to calculate the test statistic, the p-value, an

### Confidence interval for the population mean: Standard normal for workers daily wages

Pls. see attached Confidence interval for the population mean: Use of the standard normal The union for a particular industry has determined that the standard deviation of the daily wages of its workers is \$20. A random sample of 70 workers in this industry has a mean daily wage of \$120 . Find a 90% confidence interval f

### Statistics: Solve the Limits of the Confidence Interval

Confidence interval for the population mean: Use of the t distribution. A toy manufacturer wants to see how long, on average, a new toy captures children's attention. He tests 10 children selected at random and finds that their mean attention span is 33 minutes with a standard deviation of 6 minutes. If we assume that attenti

### Hypothesis Testing & Confidence Interval: Population Mean

Average cost of \$3,200 for products. n=25. After review it seems mean cost is \$2,000 with a standard deviation of \$150. Test that average cost is \$3,200 or more versus \$2,000. assume level of significance of .05. What is the null hypothesis and the alternative hypothesis? What is the critical value and the p-value? What is

### Sampling distribution, two populations: point estimate of difference in mean, std deviation

Please explain and show all calculations 1. If two large independent samples are taken from two populations, the sampling distribution of the difference between the two sample means can be determined how? 2. In my BMGT 230 class the fall semester is compared with my class 10 years ago. Please answer the following questions

### Confidence Interval and Sample Size

Piggy Bank is a ficticious company. Piggy Bank wants to estimate the mean dollars that each card holder will spend each month. It would like to be within plus or minus \$10 of the true mean with a 98% confidence level. The standard deviation is thought to be \$500. How many card holders should be sampled? After you've determined

### Allowance for error and effect of bias for newspaper reporting results of political polls

74. Many newspapers, when reporting results of political polls, say that 'with 95% confidence, the results are in error by no more than ±3 percentage points'.The typical sample size is about 1500. The allowance for error is intended to cover both sampling variability and the effect of small biases. a. Assume that the pol

### Calculation of Sample Size

7.45 A research project for an insurance company wishes to investigate the mean value of the personal property held by urban apartment renters. A previous study suggested that the population standard deviation should be roughly \$10,000. A 95% confidence interval with a width of \$1,000 (a plus or minus of \$500) is desired. How

### Confidence Interval Population Proportion: Blood type B

In a study of human blood types in nonhuman primates, a sample of 71 orangutans were tested and 14 were found to be blood type B. Construct a 95% confidence interval for the population proportion of blood type B in the orangutan population.

### 95% Confidence Interval Interpretation

Using Sample "A" Construct, (Explain and Interpret in full detail) a 90% and a 95% confidence interval for the mean of all stocks in the index based on this sample of 50 stock prices: 36.18 30.92 51.7 38.07 27.87 37.11 82.85 18.74 41.86 246.94 11.55 12 25.5 44.37 34.19 24.29 24.31 39.43 18.9 195.01 91.3 31

### Does the populations differ significantly from -150?

THE FOLLOWING DATA WAS RANDOMLY DRAWN FROM A NORMAL POPULATION. AT AN ALPHA LEVEL OF .05 DOES THE POPULATION DIFFER SIGNIFICANTLY FROM -150. USE MICRO EXCEL -86, -160, -123, -162, -103, -49, -163, -77, -174, -161

### Confidence Interval

Compute the 99% confidence interval based on four data points that have a sample mean of 71.5 and a sample standard deviation of 16.6032

### confidence interval of two population mean difference

See attached file. Determine the 95% confidence interval of the true difference in the means. A sociologist wants to determine if the life expectancy of people in Africa is less than the life expectancy of people in Asia. The data obtained is shown in the table below. Africa Asia 55.3 65.2 8.1 9.3 53 42

### Explain how to determine that research data is valid and reliable: sampling, probability

4. Using the data below, make a histogram, box plot, compute the mean, median, mode and standard deviation City and State Crime Albuquerque, NM 8515 Anaheim, CA 2827 Anchorage, AK 4370 Arlington, TX 5615 Atlanta, GA 10759 Aurora, CO 5079 Austin, TX 6406 Birmingham, AL 7030 Boston, MA 4986 Buffalo, NY 5791 Charlotte,

### 95% Confidence Interval of hypertension for younger children from drinking soda

Among children ages 5 to 15, the effects of drinking soda have profound effects on obesity. A study found 5000 children ages 5 to 10 gained significant weight and 13 developed hypertension. Among ages 11 to 15, 7 developed hypertension. What is the 95% CI for the odds ratio in favor of hypertension for younger aged children

### Confidence Interval on Population: Nurses Working 12 Hour Shift

See attached file. A survey was taken of 350 nurses and one question was asked "do you think the twelve hour shift that you work affects your job performance?" There were 237 "yes" responses. Set a 95% confidence interval on the population proportion that would respond yes.

### Explain the Central Limit Theorem; compare intervals; time to receipt of tax refund

1 Explain the Central limit theorem in your own words. What is the value of it? What assumption does one have to make when using it? 2 You have a process that has a Mean of 22.5 and a standard deviation of 5.5, taken from a sample survey of n = 25. Produce a 90% confidence interval. Produce a 99% confidence interval. Co

### Confidence Interval: Calculation and Interpretation

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) Find a

### Statistics: Estimate the average amount spent by patients at a hospital pharmacy

A marketing firm wants to estimate the average amount spent by patients at the hospital pharmacy. For a sample of 70 randomly selected patients, the mean amount spent was \$58.72 and the standard deviation \$7.60 (a) Find a 90% confidence interval for the mean amount spent by patients at the pharmacy. Show your calculations an

### Ranking Factors

Ranking Factors. In a nationwide survey of 1000 companies with more than 50 employees, managers were asked to rank various factors that influence their decisions in hiring employees. Each factor was ranked on a scale of 1 to 10, with 1 being not important and 10 being very important. The factor "educational background" re