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Confidence Interval

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

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 < ________

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


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

Confidence interval

1. A toy manufacturer wants to see how long, on average, a new toy captures children's attention. He tests children selected at random and finds that their mean attention span is minutes with a standard deviation of minutes. If we assume that attention spans are normally distributed, find a confidence interval for the mean a

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

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

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