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# Confidence Interval

### Find the confidence interval for a population proportion.

Confidence Interval I need help setting up and solving a confidence interval problem. The problem is set out below and is set out in the attached excel spread sheet. INSTRUCTION: Include a "summary statement" for each CI. PROBLEM: Find a 69% CI for the population proportion of successes when a sample of 57 had 32

### Data Analysis - Finding Sample Sizes for Confidence Intervals

INSTRUCTIONS: Include a "summary statement" for each CI. FACTS: Elected officials in a small Florida town are preparing for the annual budget for their community. Specifically, they would like to estimate how much their constituents living in this town are typically paying each year in real estate taxes. Given that the

### Confidence Interval and Mean Difference

The director of a university's development center is interested in comparing the starting annual salaries of male and female students who recently graduated form the university and commenced full-time employment. The director has formed pairs of male and female graduates with the same major and similar grade point averages. Sp

### Interpretation of Population Mean with No Standard Deviation

Estimate and interpret a population mean with the population standard deviation unknown.

### Confidence Interval, P-Value & Hypothesis Testing

See the attached file. Problem 1: A bank in a small town has 10,000 customers. A national survey on the banking habits of people in U.S. shows that 80% of the people with income higher than 50,000 dollars have both savings and checking accounts and also shows that the average number of banking operations that a person aged 18

### 90% Confidence Interval for a Population Proportion.

In a study of injuries in intermurial sports it was found that among 95 injured lacross players, 20 had read the rules of lacross. Among 875 intermural lacrosse participants 665 reported that they had read the rules of the game. Use the formula for margin of error and the z-score table to find the 90% confidence intervel estim

### 99% Confidence Interval

In a study of 90 statistics students, 14 were found to utilize a particular study strategy. Use the formula for the margin of error to answer the following: Find the 99% confidence interval estimate of the proportion of all statistic students utilizing this strategy. ________ < p < ________

### Hypothesis test, descriptive statistics, confidence intervals

Please see attached for fully formatted question. Model Model Model Model Current New Current New Current New Current New 264 277 270 272 263 274 281 283 261 269 287 259

### 95% confidence interval between the means of the two populations

Salary information regarding male and female employees of a large company is shown below. Male Female Sample Size 64 36 Sample Mean Salary (in \$1,000) 44 41 Population Variance 128 72 The 9

### Confidence interval and chi square hypothesis test for variance

A random sample of 10 observations has been drawn from a normal population, and the sample variance is found to be s^2 = 19.5. Determine the 98% confidence interval for &#61555;^2 A random sample of n = 12 is drawn from a population that is normally distributed, and the sample variance is s^2 = 19.3. Use &#61537; = 0.025 i

### Statistics: Confidence Intervals and Significance Levels

Please see the attached file for the fully formatted problems. Assignment 2: Mixed Problems 1. In your own words explain the difference between a point estimate and an interval estimate of a parameter? Which is better? Why? Answer: The point estimate is the value that is specific and is a single number of a paramete

### Statistics - Population Variance - Confidence Interval

The grades of a sample of 5 students, selected from a large population, are given below. Grade 70 80 60 90 75 a. Determine a point estimate for the variance of the population. b. Determine a 95% confidence interval for the variance of the population. c. At 90% confidence, test to determine if the variance of the populat

### Yellow Pages ...

A sample of 20 pages was taken without replacement from the 1,591-page phone directory Ameritech Pages Plus Yellow Pages. On each page, the mean area devoted to display ads was measured (a display ad is a large block of multicolored illustrations, maps, and text). The data (in square millimeters) are shown below: 0 260 356 403

### Normality

Biting an unpoped kernel of popcorn hurts! As an experiment a self-confessed connoisseur of cheap popcorn carefully counted 773 kernels and puts them in a popper. After popping, the unpopped kernels were counted. There were 86. (a) Construct a 90 percent confidence interval for the proportion of all kernels that would not pop

### Inference from Two Samples: hypothesis tests and confidence intervals.

Heights of Winners and Runners-Up Listed below are the heights of candidates who won presidential elections and the heights of the candidates with the next highest number of popular votes. The data are in chronological order, so the corresponding heights from the two lists are matched. For candidates who won more than once, o

### Confidence Intervals of the Difference Between Population Means

In these two exercises, assume that the two samples are independent random samples selected from normally distributed populations. Do not assume that the population standard deviations are equal, unless stipulates otherwise. The Confidence Interval for Comparing Diets A randomized trial tested the effectiveness of diets o

### Find confidence intervals for discrete distributions.

A. Let p equal the proportion of letters mailed in the Netherlands that are delivered the next day. If y= 142 out of a random sample of n=200 letters were delivered the day after they were mailed, find an approximate 95% confidence interval for p. B. Let p equal the proportion of Americans who favor the death penalty. If a ra

### Construct a hypothesis test to determine whether the number of vehicle occupants is related to vehicle speed.

Safety researchers, interested in determining whether the occupancy of a vehicle might be related to the speed at which the vehicle is driven, have observed the following speed (mph) measurements from two random samples of vehicles (use data file xr12030) Driver alone 64 50 71 55 67 61 80 56 59 74 At least one Passen

### Construct a confidence interval for a proportion based on the results of a sample survey.

An airline has surveyed a simple random sample of air travelers to find out whether they would be interested in paying a higher fare in order to have access to e-mail during their flight. Over the 400 travelers surveyed, 80 said e-mail access would be worth a slight extra cost. Construct a 95% confidence interval for the po

### A 98% confidence interval estimate for the population mean of individual credit card charges would be.

An auditor for a large oil corporation has taken a random sample of monthly credit card charges for 32 individual (non-corporate) accounts. She found a mean of \$81.76. Assume that the population standard deviation is 48.2. A 98% confidence interval estimate for the population mean of individual credit card charges would be. a.

### A consumer magazine has contracted a simple random sample of 33 owners of a certain model of automat bile and asked each owner how many defects had to be corrected within the first 2 months of owners

A consumer magazine has contracted a simple random sample of 33 owners of a certain model of automat bile and asked each owner how many defects had to be corrected within the first 2 months of ownership. The average number of defect was x-bar = 3.7, with a standard deviation of 1.8 defects. a. Use the t distribution to constru

### Confidence interval: population proportion survey

Based on its 1999 survey, Student Monitor reports that 20% of U.S. college students used the Internet for job hunting during the month preceding the survey. Assuming this finding to be based on a simple random sample of 1600 college students, construct an interpret the 90% confidence interval for the population proportion of col

### Confidence interval: population proportion...

An airline has surveyed a simple random sample of air travelers to find out whether they would be interested in paying a higher fare in order to have access to e-mail during their flight. Over the 400 travelers surveyed, 80 said e-mail access would be worth a slight extra cost. Construct a 95% confidence interval for the popula

### Statistics - Point Estimate ...

A survey of 600 randomly selected people reveals that 384 of them think that the President of the United States is doing a good job regarding domestic issues. a. What is the point estimate and what does this mean? b. What is the 95% confidence interval to estimate the true proportion of people who think the president is do

### Finding Confidence Intervals

Minting Quarters Quarters are currently minted with weights having a mean of 5.760 g and a standard deviation of 0.062 g. New equipment is being tested in an attempt to improve quality by reducing variation. A simple random sample of 24 quarters is obtained from those manufactured with the new equipment, and this sample has a

### Comparing Means with Confidence Intervals

Maximum breadths of samples of male Egyptian skulls from 4000 B.C. and 150 A.D. (based on data from Ancient Races of the Thebaid by Thomas and Randall-Maciver): 4000 B.C.: 131 119 138 125 129 126 131 132 126 128 128 131 150 A.D.: 136 130 126 126 139 141 137 138

### Shoveling Heart Rates. Find and interpret confidence intervals for the mean.

Shoveling Heart Rates Because cardiac deaths appear to increase after heavy snowfalls, an experiment was designed to compare cardiac demands of snow shoveling to those of using an electric snow thrower. Ten subjects cleared tracts of snow using both methods, and their maximum heart rates (beat per minute) were recorded during

### Cotinine Levels of Smokers. Find and interpret a confidence interval for the mean.

Cotinine Levels of Smokers When people smoke, the nicotine they absorb is converted to cotinine, which can be measured. A sample of 40 smokers has a mean cotinine level of 172.5. Assume that the population standard deviation is known to be 119.5, find a 90% confidence interval estimate of the mean cotinine level of all smoker

### Estimating the Mean - Hypothesis Test

If 45 officials in student services earned an average of x(with a line over it) = \$50,340 each year: a. Assume that the standard deviation is 16,920 for salaries of officials. Find the 90% confidence interval for the population mean salary of such personal. What is the margin of error. b. If SD is 10,780, Find the 90% conf

### Test Tires Using a 95% Confidence Interval of Average Mileage

"Joe" is he shop manager at a truck line and is approached by a salesman about some new tires. The salesman assures Joe that the tires will get an average of 60,000 miles before wearing out. Not being that gullible Joe asks for 100 tires for a test. The tires are mounted and run to wear-out and the 95% confidence interval of