Share
Explore BrainMass

# Confidence Interval

### Using and Interpreting Concepts

An election poll reported that a candidate had an approval rating of 48% with a margin of error E of 3%. Construct a confidence interval for the proportion of adults who approve of the candidate. You are a travel agent and wish to estimate, with 95% confidence, the proportion of vacationers who plan to travel outside the Unit

### Population Proportion, Estimation and Confidence Levels

As a condition of employment, Fashion Industries applicants must pass a drug test. Of the last 220 applicants 14 failed the test. Develop a 99 percent confidence interval for the proportion of applicants that fail the test. Would it be reasonable to conclude that more than 10 percent of the applicants are now failing the test? I

### Cnfidence Interval & Sample Size: Population Proportion

In a survey of 1037 adults from the United States age 65 and over, 643 were concerned about getting the flu. (Source: Harvard School for Public Health). (a) Find a point estimate for the population proportion p of those concerned about getting the flu. Answer: (b) Construct a 90% confidence interval for the population

### Data Analysis

THis is a masters level stastics class. Need ehlp with data analysis. Not sure I understand what is being asked. This is a subject I am not strong in. The data that you will be using for this exercise came from a survey of two insurance carriers. The first carrier (C1) was compared against the second competi

### Biting an unpopped kernel of popcorn hurts!

Biting an unpopped kernel of popcorn hurts! As an experiment, a self-confessed connoesseur of cheap popcorn carefully counted 773 kernels and put 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.

### Statistics - Random sample and confidence interval

You are given the sample mean and the sample deviation, Use this information to construct the 90% and 95% confidence intervals for the population mean. Which interval is wider? A random sample of 38 gas grills has a mean price of \$638.20 and a standard deviation of \$59.80. a)The 90% confidence interval is __,__ (round

### Confidence Intervals and Estimates

A survey of 85 families showed that 36 owned at least one DVD player. Find the 99% confidence interval estimate of the true proportion of families who own at least on DVD player. Lower limit= Upper limit=

### Confidence intervals for pharmacy customers

A random sample of 16 pharmacy customers showed the waiting times below in minutes. Find a 90 percent interval for u, assuming that the sample is from a normal population. 21 22 22 17 21 17 23 20 20 24 9 22 16 21 22 21

### Confidence Interval for Proportion and Sample Size

Determine the percentage of Fortune 500 CEO's who think Main University deserves its current popular magazine rating. All 500 CEO's receive a questionnaire and only 100 respond. Exactly half of the respondents believe the ranking is deserved. a) construct a 99% confidence interval for the fraction of Fortune 500 CEO's who bel

### Confidence interval and t-distributions

In a random sample of 62 bolts, the mean length was 1.87 inches and the standard deviation was 0.07 inch. Use a normal distribution or a t-distribution to construct a 90% confidence interval or the mean. Which distribution should be used to construct the 90% confidence interval? A. Use a normal distribution because the len

### Confidence Interval for Election Polls

An election poll reported that a candidate had an approval rating of 30% with a margin of error E of 4%. Construct a confidence interval for the proportion of adults who approve of the candidate. The confidence interval for the proportion o adults who approve of the candidate is (______,______) Round to two decimal places as

### Sample Mean, Standard Deviation & Confidence Interval

The State test scores for 12 randomly select High School Senior are shown below: "Assume the population is normally distributed" 1425 1227 985 699 723 837 726 744 542 621 1445 949 a) Find the Sample Mean _ X = ________ Round to one decimal place as needed b) Find the Sample Standard Deviation

### Confidence Interval for Election Polls

An election poll reported that a candidate had an approval rating of 30% with a margin of error E of 4%. Construct a confidence interval for the proportion of the adults who approve of the candidate. The confidence interval for the proportion of adults who approve of the candidate is ( , ). round to two decimal places as

### Confidence Interval for Population Mean

In a random sample of six microwave ovens, the mean repair cost was \$90.00 and the standard deviation was \$11.00. Assume the variable is normally distributed and use a t-distribution to construct a 90% confidence interval for the population mean u. What is the margin of error of u? The 90% confidence interval for the popula

### Confidence Level: The Number of Books

Question: People were polled on how many books they read the previous year. How many subject are needed to estimate the number of books read the previous year within one book with 99% confidence? Initial survey results indicate that o=11.7 books. A 99% confidence level requires (_______) subjects.

### 11 Probability questions

Find the indicated probability or percentage for the normally distributed variable. 1) The variable X is normally distributed.The mean is &#956; = 22.0 and the standard deviation is &#56256;&#57239; = 2.4. 1) Find P(19.7 < X < 25.3). A) 0.4107 B) 1.0847 C) 0.3370 D) 0.7477 2) The incomes of trainees at a local mill are n

### Finding Margin of error and Confidence Interval

Find the critical value Zc necessary to form a confidence interval at the given level of confidence. The new Twinkle bulb has a mean life of hours with a standard deviation Q = 35 hours. A random sample of 50 light bulbs is selected from inventory. The sample mean was found to be X(with a line above X) 500 hours. a.Find

### Confidence interval for mean ..

Confidence Intervals for the Mean (Small Samples) An experimental egg farm is raising chickens to produce low cholesterol eggs. A lab tested 16 randomly selected eggs and found that the mean amount of cholesterol was X(with line above the X) = 190 mg. The sample standard deviation was found to be s = 18.0 mg on this group

### Confidence interval for population proportion

Confidence Intervals for Population Proportions 5.The new Twinkle bulb is being developed to last more than 1000 hours. A random sample of 100 of these new bulbs is selected from the production line. It was found that 64 lasted more than 1000 hours. Find the point estimate for the population proportion, the margin of error fo

### Levels of Confidence and Intervals

1. Find the level of confidence assigned to an interval estimate of the mean formed using the interval: x − 1.96⋅σx to x + 1.96⋅σ x . 2. The lengths of 225 fish caught in Lake Michigan had a mean of 15.0 inches. Assume that the population standard deviation is 2.5 inches. - Give a point estimate for μ . - F

### Interval estimates and differences

1. What is the difference between a point estimate and an interval estimate of a parameter? Which is better? Why? 2. What information is necessary to calculate a confidence interval? Is the size of the population relevant when one is determining the sample size for a confidence interval? What is necessary to determine the samp

### Solve: Confidence Interval for the Mean

Scenario: A study of 35 golfers showed that their average score on a particular course was 92. The standard deviation of the sample is 5. Solve the following questions: Find the best point estimate of the mean. Find the 95% confidence interval of the mean score for all golfers. Find the 95% confidence interval of the mean

### Confidence Intervals in Normality

Suppose that for a small sample of n = 11 measurements, we find that x- = 72 and s = 5. Assuming normality, compute confidence intervals for the population mean u with the following levels of confidence. a. 95% b. 99% c. 80% d. 90% e. 98% f. 99.8%

### Determining Confidence Level

"A higher confidence level may or may not lead to a wider confidence interval." Briefly state how you would determine what confidence level (e.g. 90%, 95% or 99%) suits your purpose. You may use a suitable example to explain your ideas.

### Using the data given, find the time of day that has the shortest commute time.

I need to measure minutes to and from work versus the time of day I leave. The objective is to find the time of the day that takes the least amount of time to get to work from the data given. I would like the results to include a bell curve if possible. What would be the best form of measure: linear regression or null hypot

### Families USA Confidence Interval

Families USA, a monthly magazine that discusses issues related to health and health costs, surveyed 20 of its subscribers. It found that the annual health insurance premiums for a family with coverage through an employer averaged \$10,979. The standard deviation of the sample was \$1,000. a. Based on this sample information, deve

### Statistical Process Control applied to data on feeding a dog through a Control Chart

I need data for 4 weeks. The statistical process control process is feeding a dog. This is a process I do but must spend less time doing based on Statistical Control is a method to help you know when your process is out of control. I must make up data for Week One ending on June 22. Week 2 ending on June 29. Week 3 ending on Jul

### Question

1, how large a sample sample should one select to be 86% confident that the sampling error is 10 or less? assume that the population standard deviation is 250. 2, a simple random sample of 500 provides 100 yes responses. compute the 94% confidence interval for the population proportion.

### Confidence interval for mean

3. in an effort to estimate the annual income for new graduates, data were collected from 500 new graduates over a one -year period. assume a population standard deviation of \$500. a) if the sample mean is \$15,000, what is the 95% confidence interval for the population mean? b) if the sample mean is \$15,000, what is the 98

### Confidence

9.4 An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 40 hours. If a sample of 30 bulbs has an average life of 780 hours, find a 96% confidence interval for the population mean of all bulbs produced by this firm. 9.6 The heights of a