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Confidence Interval

Sample Size and Confidence Intervals in Statistical Analysis

If a random sample of 10 people found that 9 were pro-life (i.e., 90%), while another random sample of 1000 people from the same population found that 550 were pro-life (i.e. 55%), which would you find to be more significant? Why? When pollsters report results of a poll, they often include the margin of error but not much m

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

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

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

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

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

Find regression lline and confidence interval

Question 1: Suppose we have the following information from a simple regression: -What is the coefficient of determination?? -What is the correlation coefficient? -What is the sample mean of Y?? -Test the hypothesis vs. , with ? = 0.05.   Question 2: survey 35 students and find that the mean daily spending is $63.57 with a

Jacob Lee Flight Times

Jacob Lee is a frequent traveler between Los Angeles and San Francisco. For the past month, he wrote down the flight times on three different airlines. The results are found in the attachment. a. Use the .05 significance level and the five-step hypothesis-testing process to check if there is a difference in the mean flight ti

Newt Dimswitch: Construction Crew

Newt Dimswitch owns a small construction company in Chesapeake, Virginia. He often uses more than one construction crew, and has had a difficult time maintaining records on profit levels, cost controls, and other variables that are necessary in making business decisions. Newt somehow feels that the use of one of his construction

How to Find Confidence Interval and Perfrom One Tailed T Test

Let x be a random variable representing percetage of carboxyhemoglobin in the blood. For a person who is a regular heavy smoker, x has a distribution that is approximately normal. A random sample of n= 12 blood test given to a heavy smoker gave the following results: 9.1 9.5 10.2 9.8 11.3 12.2 11.6 10.3 8.9 9.7 13.4 9.9 a

Cumulative weight loss: propranolol treatment

The following table presents the mean cumulative weight loss (in grams) for 30 patients receiving propranolol (treatment) and for 60 control patients following sweating during insulin-induced hypoglycemia. Mean loss weight compared between treatment and control for 90 patients during insulin-induced hypoglycemia Intervention

Statistics Problem Set and the Standard Normal Distribution

1. (TCO 6) In the standard normal distribution, the variance is always 0 1 2 none of these 2. (TCO 6) The area under the standard normal curve is 0 1 2 none of these 3. (TCO 6) If John gets an 80 on a physics test where the mean is 85 and the stan


Statistics - Lab #6 Statistical Concepts: Data Simulation Discrete Probability Distribution Confidence Intervals Calculations for a set of variables Open the class survey results that were entered into the MINITAB worksheet. We want to calculate the mean for the 10 rolls of the die for each student in the class.

Statistic problems

1. The U.S. Department of Transportation reported the results of a survey of driving safety. In a random sample of 900 drivers, 425 were using their cell phone. Compute,and explain, a 95% confidence interval estimate of the population proportion of drivers who use their cell phone while driving. 2. Grades on a final exam in S

Case Analysis: Using data to make decisions about honeymoon destinations.

To complete this assignment, use to the "Honeymoon Destinations" reading from your studies for this unit, and the Honeymoon Destinations Code-book Excel file and the Honeymoon Destinations Code-book Errata document linked in the Resources. Note that there are three discrepancies between the data in the case code book from the re

Confidence Levels and P-Values

1) In a survey conducted to determine the cost of vacations, 64 individuals were randomly sampled. Each person was asked the cost of her or his most recent vacation and the sample mean was computed as $1810.16. Assuming that the population standard deviation is $400, estimate with 95% confidence the average cost of all vacations

Confidence Interval and Sample Size in HR Departments

1.) A sample of 35 different HR departments found that employees worked an average of 240.6 days a year. If the population standard deviation is 18.8 days, find the 90% confidence interval for the average number of days ? worked by all employees of these HR departments. A) 230.9 < ? < 250.3 B) 236.8 < ? < 244.4 C) 232.4 < ? <

Confidence Interval.

FedEx and United Parcel Service (UPS) are the world's leading cargo carriers by volume and revenue (The Wall Street Journal, January 27, 2004). According to the Airports Council International, the Memphis International Airport (FedEx) and the Louisville International Airport (UPS) are two of the ten largest cargo airports in the

95% Confidence interval

The Minneapolis Star Tribune newspaper has decided to write an article about gasoline prices in the Twin Cities area (Minneapolis and St. Paul). The paper has designed a survey and taken a simple random sample of regular, unleaded gas prices at 35 area stations. The results are in the Area Gas Prices - Random Sample Excel file.

Constructing a 95% confidence interval

If x bar =75, S = 24, and n = 36, and assuming that the population is normally distributed, construct a 95% confidence interval estimate of the population mean, µ.

Explanation of Confidence Interval

Randomly selected students participated in an experiment to test their ability to determine when one minute (or sixty seconds) has passed. Forty student yielded a sample mean of 61.8 seconds. Assuming that the standard deviation = 8.1 seconds, construct and interpret a 99% confidence interval estimate of the population mean of a