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# Confidence Interval

### Confidence Interval Estimate, Hypotheses and Test Statistics

1. Mimi was the 5th seed in 2012 UMUC Tennis Open that took place in August. In this tournament, she won 83 of her 100 serving games. Based on UMUC Sports Network, she wins 80% of the serving games in her 5-year tennis career. (a) Find a 95% confidence interval estimate of the proportion of serving games Mimi won. (Show wor

### Null Hypothesis and Confidence Interval

Please see the attachment for the fully formatted solution. The Osborne manufacture makes a soft drink dispensing machine that allows customers to get soft drinks from the machine in a cup with ice. When the machine is running properly, the average number of fluid ounces in the cup should be 14. Periodically the machines need

### Confidence Interval Construction

Question: June Walker is the Director of the Annual Fund for Marine Life University. She asks her analyst to study the giving patterns of the alumni of the School of Marine Sciences. Her analyst collects a random sample of 44 records and calculates an average annual participation in the Fund of 10.455 years. The standard deviat

### Statistics Coefficient Importance

DQ 1 If we wish to have a 95% confidence interval, what would be the value of the confidence coefficient? [Hint: Table 4B] DQ 2 In your own words, describe the relationship between the standard error (of the mean) and maximum error. The standard error is the standard deviation. The maximum error is the product of the s

### Finding the interval estimates for true sales

In the second 14 weeks of the Books R Use data, the mean total sales were \$19,543. The standard deviation was \$11,502. At the .05 level of significance, what was the confidence interval? Did the value \$16,400 fall inside our outside the confidence interval?

### Confidence Intervals of Population Mean

According to a report produced by the New South Wales Ministry of Health, 46% of hospitalisations occur in people aged sixty years and over (60+). You randomly select forty people who were hospitalized in the past year and find that fifteen of them are 60+. a) Perform a hypothesis test at the 5% level of significance that 46

### Statistics and Confidence Intervals

John Kim is the purchasing manager for your computer, Inc., a manufacture of network servers. A truckload of sheet metal has just arrived. Previous experience with the supplier suggests that the thickness of the sheet metal follows a normal distribution. A random sample of 23 sheets yields an average thickness of 0.192 inches

### Constructing Confidence Intervals

10. Construct the 95% confidence interval for B and M, of the regression line y = Mx + B, for the population using the following inequalities and data. Use the below data, and complete parts a and b. (see attachment) a) Construct the 95% confidence interval for the population y-intercept, B. ___ < B < ___ (round to th

### Statistical Case and Management Report

I need help for the study case attached.

### Constructing the confidence interval for mean

The following data values are a simple random sample from a population that's normally distributed with (symbol for variance) o2=4.0: 11,6,8,12 and 13. Construct and interpret the 90% and 95% confidence intervals for the population mean.

### Essentials of Marketing Research, William R. Dillon, Thomas J.

In the book Essentials of Marketing Research, William R. Dillon, Thomas J. Madden, and Neil H.Firtle discuss a survey of marketing professionals, the results of which were originally published by Ishmael P. Akoah and Edward A. Riordan in the Journal of Marketing Research. In the study, randomly selected marketing researchers wer

### MCQs: Confidence Intervals

1. A sample of n=9 college students is used to evaluate the effectiveness of a new Study Skills Workshop. Each student's grade point average (GPA) is recorded for the semester before the workshop and for the semester after the workshop. The average GPA improved by MD = 0.60 points with s2 = 0.09. The researcher would like to us

Using a situation involving children who are diagnosed with ADHD who are treating with an experimental drug for ADHD, describe how this situation could be addressed using a one-way analysis of variance (ANOVA). For this situation, clearly state the independent and dependent variables of the study (making sure to state the number

### Independent Samples - Dealing With Self-Esteem

Numerous studies have found that males report higher self-esteem than females, especially for adolescents (Kling, Hyde, Showers, & Buswell, 1999). Typical results show a mean self-esteem score of M=39.0 with SS=60.2 for a sample of n=10 male adolescents and a mean of M=35.4 with SS=69.4 for a sample of n=10 female adolescents.

### T-Test on animals

Many animals, including humans, tend to avoid direct eye contact and even patterns that look like eyes. Some insects, including moths, have evolved eye-spot patterns on their wings to help ward off predators. Scaife (1976) reports a study examining how eye-spot patterns affect the behavior of birds. In the study, the birds were

### How to Find Margin of Error for Confidence Intervals

A researcher wishes to estimate the proportion of college students who cheat on exams. A poll of 490 college students showed that 33% of them had, or intended to, cheat on examinations. Find the margin of error for the 95% confidence interval.

### A sample of 64 statistics students at a small college had a mean mathematics ACT score of 28 with a standard deviation of 4.

A sample of 64 statistics students at a small college had a mean mathematics ACT score of 28 with a standard deviation of 4. Estimate the mean mathematics ACT score for all statistics students at this college. Give the 95% confidence interval.

### Interpreting the Confidence Interval

The U.S. Food and Drug Administration (FDA) performed a study that compared the carbohydrate content (as a percentage of weight) of several major brands of corn and potato chips. Fourteen brands of corn chips were sampled and 14 brands of potato chips were sampled. Data was collected and the following 95% confidence interval was

### Qualitative Analysis: Confidence Intervals

Annual family dental expenses for the families of a random sample of ten employees of a company are given below. You can assume the family dental expenses for the employees of the company are normally distributed. \$450, \$390, \$550, \$140, \$690, \$600, \$250, \$330, \$490, \$810 a) Compute the mean and standard deviation of the sam

### Calculating Standard Deviations and Confidence Intervals.

The following table (see problem #7 on page 310 of attachment) lists the results of one question taken from a survey conducted for Joe's Bar and Grill. The Grill has recently undergone renovations, and with the new look, management has decided to change the menu. They are interested in knowing how well customers like the new men

### Descriptive Statistics Interpreting Data Sets

The data on the left is the level of GDP freedom for 42 nations 1. Run descriptive statistics on this data set and interpret the meaning (this does not mean just repeating the numbers) 2. Create a 90%, 95%, and 99% confidence interval and explain what this means 3. Do a hypothesis test and check to see if a value of a s

### Confidence Interval Concepts

Consider the formula used for any confidence interval and the elements included in that formula. What happens to the confidence interval if you (a) increase the confidence level, (b) increase the sample size, or (c) increase the margin of error? Only consider one of these changes at a time. Explain your answer with words and by

### Interpreting Confidence Interval

I need help with the following questions: 1. A simple random sample of 40 salaries of NCAA football coaches has a mean of \$415,953 and a standard deviation of \$463,364. Construct a 95% confidence interval estimate of the mean salary of an NCAA football coach. 2. In a study designed to test the effectiveness of acupuncture

### Find 95% confidence interval for variance and standard deviation

You randomly select and measure the contents of 10 bottles of cough syrup. The results are listed 4.212 4.298 4.259 4.243 4.181 4.209 4.269 4.244 4.223 4.237 Assume sample is taken from normally distributed population. Construct 95% confidence intervals for: (a) Confidence interval for population variance ____,__

### Finding the Width for the Confidence Intervals

The owner of Limp Pines Resort wanted to know the average age of its clients. A random sample of 25 tourists is taken. It shows a mean age of 46 years with a standard deviation of 5 years. The width of a 98 percent CI for the true mean client age is approximately ____ years. In a sample size calculation for a mean, if the confid

### Finding the minimal size based on margin of error

A researcher wishes to estimate with 90% confidence, with percentage of adults wishing to abolish pennies. Estimate must be accurate within 2% of true proportion. Find the minimum sample size needed using study that found 26% respondents that support abolishing pennies. (a) Find minimum sample size needed (b) No preliminar

### Finding Confidence Interval for Variance and Standard Deviation

Please provide help with home work problems constructing 95% C.I. (a) Find confidence interval for the populaton variance is (round six decimals). (b) The confidence interval for the population standard deviation is? Round four decimal places You randomly select and measure 10 bottles of cough syrup, the results (

### Statistics - Confidence Intervals

I need help completing this question: A sample of 64 statistics students at a small college had a mean mathematics ACT score of 28 with a standard deviation of 4. Estimate the mean mathematics ACT score for all statistics students at this college. Give the 95% confidence interval. Thank you for your assistance.

### Proportion, Sample, and Confidence Interval Problem

I need help coing up with solutions for the following problem: For many of us a person aged 80 years is considered "old." However, for legal purposes involving the establishment of age discrimination, 40 is typically considered the magic number. In fact, cases are won or lost based on the proportion of workers employed who

### Level of confidence

What role does the level of confidence play in an interval estimate? Can you help me understand? An example would also be helpful.