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# Confidence Interval

### Normal Probability, Samples and Confidence intervals

1- The EMT industry reports that the average time it takes to respond to an emergency call is 25 minutes. Assume that is time is normally distributed with a sigma of 4 minutes. What percentage of call will be responded to in less than 20 minutes? 2- To qualify for the Police Academy, a candidate must score the top 15% on the

### Statistical inferences for two populations, matched pairs test, F test, variances, ANOVA

See attached file. I do not have the capabilty to use Microsoft Word's Equation Editor and on some of these questions the "x" should have a line over it. 1. Write a hypothesis to test the differences between two populations. 2. (STATISTICAL INFERENCES ABOUT TWO POPULATIONS) Use the following sample information to co

### 10 Problems on Descriptive Statistics, Point Estimates and Confidence Interval

1. Use the confidence interval to find the estimated margin error. Then find the sample mean. A biologist reports a confidence interval of (1.8, 3.0) when estimating the mean height (in centimeters) of a sample of seedlings. The estimated margin of error is______. The sample mean is _________. 2. You work for a consume

### Simulations of confidence intervals: simulate 5000 intervals and note proportion that contained the mean

Confidence intervals are used to help you get a better feel for your estimated value. Confidence intervals are like nets. You don't know what the TRUE proportion value is so you throw a net (find a confidence interval based upon a survey). The confidence level indicates the percentage of times your net would "catch" the true pop

### Constructing confidence intervals

We will be constructing confidence intervals for the proportion of each color as well as the mean number of candies per bag. Use the methods of 6.3 for the proportions and 6.1 for the mean. If calculating by hand, be sure to keep at least 4-6 decimal places for the sample proportions to eliminate large rounding errors.

### Margin of error and the confidence interval

6.10 Margin of error and the confidence interval. A study based on a sample of size 25 reported a mean of 93 with a margin of error of 11 for 95% confidence. (a) Give the 95% confidence interval. (b) If you wanted 99% confidence for the same study, would your margin of error be greater than, equal to, or less than 11? Expl

### Calculation of Confidence Interval and Sample Size

Please show work, step by step. 1) Suppose a fast food restaurant wishes to estimate average sales volume for a new menu item. The restaurant has analyzed the sales of the item at a similar outlet and observed the following results: X = 500 (mean daily sales) s = 100 (standard deviation of sample) n = 50 (sample size)

### Confidence Interval for Mean: Baseball Data

Please see the attached spreadsheet: With the data I need to answer the following: A)Develop a 95 percent confidence interval for the mean number of home runs per team B)develop a 95 percent confidence interval for the mean number f errors committed by each team C) Develop a 9 percent confidence interval for the mean

### Random sample of UCU customers who balance their accounts in a timely manner

5. The manager of University Credit Union (UCU) is concerned about checking account transaction discrepancies. Customers are bringing transaction errors to the attention of the bank's staff several months after they occur. The manager would like to know what proportion of his customers balance their checking

### Question about Confidence Interval & Sample size

1. A promotion campaign is being planned to encourage people to reduce heat in their homes. In order to measure the campaigns impact, we want to determine the proportion of people who reduce their heat at night. A telephone sample will be taken before and after the campaign. A. What sample size is required if an accuracy of +/-

### Proportion, confidence level, standard deviation, population variance

Please see attached 14 Questions. 1. An auditor wants to estimate what proportion of a bank's commercial loan files are incomplete. The auditor randomly samples 100 files and finds 9 are incomplete. Using a 95% confidence interval, estimate the true proportion of incomplete files for ALL the bank's commercial loans. 2.

### Construct a confidence interval for difference in two teams unacceptable auto assemblies

Two teams of workers assemble automobile engines at a manufacturing plant in Michigan. Quality control personnel inspect a random sample of the teams assemblies and judge each assembly to be acceptable or unacceptable. A random sample of 127 assemblies from team 1 shows 12 unacceptable assemblies. A similar random sample of 9

### M&M project: Construct a 95% Confidence Interval for Proportion

M&M Project: Part 3 Use the M&M data to complete this assignment. StatCrunch can be used to assist with the calculations. A link for StatCrunch can be found under Tools for Success in Course Home. Here is also a link: http://statcrunch.pearsoncmg.com/statcrunch/larson_les4e/dataset/index.html. Submit your answers in Exce

### Statistics: Five Word Problems

1) The owner of a fish market has an assistant who has determined that the weights of catfish are normally distributed, with mean of 3.2 pounds and standard deviation of 0.8 pound. What percentage of samples of 4 fish will have sample means between 3.0 and 4.0 pounds? 2) A survey of working women in North America was conduct

### Statistics: Problems

1. For a t distribution with 16 degrees of freedom, find the area, or probability, in each region. a. To the right of 2.120. (Use 3 decimals.) __________ b. To the left of 1.337. (Use 2 decimals.) __________ c. To the left of -1.746. (Use 2 decimals.) __________ d. To the right of 2.583. (Use 2 decima

### Statistics: Types of estimates, z value, random samples, confidence interval, t value

1. Katherine Tao, Director of Marketing Research, is evaluating consumer acceptance of a new toothpaste package. Her staff reports that 17% of a random sample of 200 households prefers the new package to all other package designs. If Katherine concludes that 17% of all households prefer the new package, she is using a _______.

### Statistics: descriptive or inferential, classify data, variance, deviation, distribution

NOTE: Please ensure that when applicable all computations are clearly provided to indicate how you arrived at your final response. Failure to do so will result in a loss of half the allotted marks for the problem in question. 1. Identify each of the following statistics as either descriptive or inferential: a). Seventy-thr

### Confidence Interval and Power of a Test

On 10 leases on the outer continental shelf in the Gulf of Mexico in 1984, Atlantic Richfield submitted bids. The bids are given below: 14.27, 14.60, 14.98, 15.25, 15.30, 15.42, 15.50, 15.72, 15.83, and 15.92. The x(mean)=15.279 and the s=.532. Assume that these bids are normally distributed. Place a 95% two sided confidence

### Confidence Interval Estimate for absentism among clerical workers

The personnel director of a large corporation wished to study absenteeism among clerical workers at the corporation's central office during the year. A random sample of 25 clerical workers reveals the following: Absenteeism: X= 9.7 days, S = 4.0 days 12 clerical workers were absent more than 10 days A. Construct a 95% c

### Statistics problems: Ground coffee, H&R Block, NY savings banks, 2-liter bottle, Cumba

See attached files. 1.) In a recent year, about two-thirds of the U.S. households purchased ground coffee. Consider the annual ground coffee expenditures for households purchasing ground coffee, assuming that these expenditures are approximately distributed as a random normal variable with a mean of \$65.16 and a standard devi

### Margin of Error

Chapter 7 - Section 2 Problem 20 Finding Margin of Error. Assume that a sample is used to estimate a population proportion p. Find the margin of error E that corresponds to the given statistics and confidence level. 90% confidence; the sample size is 1780, of which 35% are successes. Problem 30 Gender Selection

### Statistics: Confidence Interval for the Scribe's use of caffeine

Confidence Interval or the lack of it... It is the year 1581 A.D. At the Renaissance University (RU), I am the appointed CPA, Coffee Pot Attendant. It is a very important office sponsored by the Head Scribe. I have taken this job very seriously, because I believe that I am the key to increased productivity of scribes at

### Statistics: Chapter 7 and 8 problems

See attached file. Chapter 7, problems 7.22, 7.23, 7.24, 7.25 Chapter 8, problems 8.32, 8.33, 8.61, 8.67 7.22. The US Census Bureau announces that the median sales price of new houses sold in March 2006 was \$224,200 while the mean sales price was \$ 279,100. Assume that the standard deviation of the prices is \$ 90,000.

### Basic Statistics Questions: Population mean, confidence interval, standard deviation, sample proportion, z-value, sample size

1. (TCO 7) Interpret a 99% confidence interval of (5.355, 5.445) for a population mean. 2. (TCO 7) A nursing school wants to estimate the true mean annual income of its alumni. It randomly samples 200 of its alumni. The mean annual income was \$55,200 with a standard deviation of \$1,500. Find a 95% confidence interval for

### Hypothesis Testing & Confidence Interval Sample Errors

Consider that 10 observations were selected from a normal population whose variance is 64. Observations are: 58, 62, 45, 50, 59, 65, 39, 40, 41 and 52. Check to 5% (.05) level of significance if there is sufficient evidence to conclude that the average population is 45. Calculate the sample average. Calculate the standard

### confidence interval of 10 miniature Tootsie Rolls' weight

A random sample of 10 miniature Tootsie Rolls was taken from a bag. Each piece was weighted on a very accurate scale. The results in grams were: a. 3.087 b. 3.131 c. 3.241 d. 3.241 e. 3.270 f. 3.353 g. 3.400 h. 3.411 i. 3.437 j. 3.477 (a) Construct a 90 percent confidence interval for the true mean weight. (b

### Confidence interval estimation.

In a certain region of the country, average radar echo duration of lightning flashes is .81 sec and a standard deviation of .34 sec. Note, that these are population values. Calculate a 99% (two sided) confidence interval for the true average echo duration ? , for a random sample of 100 lightening flashes

### Sample Size and Probability

1 ) Management has asked a lab to produce accurate results at the 88% level for a first time experiment. the management wants the final error to be within 1/10th of the sample standard deviation. Find the sample size. 2) A sample of 16 women had a mean score of 275 and a variance value of 360. A. find both the 955 and 99

### T-distribution or CLT: Two sided interval analysis on test score

Assume a very large normally distributed population of scores on a test with mean 77 and standard deviation 7. a. Find the two sided interval that includes 90% of this population b. Suppose a sample of 40 members is randomly selected from this population. Find an interval (two sided) that provides a 5% error in the estimat

### ElecMart: Two sided confidence intervals fo customers' orders

See attached data file. Problem (P_Data on the template) contains data for 400 customers. This company, ElecMart sells electronic appliances for mail-in orders. Consider this data as a random sample from all of ElecMart mail-in orders. Find the following two sided confidence intervals: a. Find the 95% Confidence Inter