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# Confidence Interval

### Minimum Sample Size for Implementing an Honor Code

Preliminary estimated suggest that about 58% of students at a state university favor implementing an honor code. To obtain a 95% confidence interval for the proportion of all students at the university favoring the honor code, what is the minimum sample size needed if the total width of the confidence interval must be less than

### Confidence Interval

2. We are interested in purchasing a large collection of Palm M515 PDAs but need to have a general idea of how much we must pay for budgetary purposes. Thus, we will construct a confidence interval on the purchase price and in doing so we will assume that selling prices are close to being normally distributed. A sample of selli

### Confidence Interval Program

Assume you need to build a confidence interval for a population mean within some given situation. Naturally, you must determine whether you should use either the t-distribution or the z-distribution or possibly even neither based upon the information known/collected in the situation. Thus, based upon the given information for

### Confidence Interval For Effect Of Birth Weight On IQ Score

Please help with the following. Confidence Interval for Effect of Birth Weight on IQ Score: When investigating a relationship between birth weight and IQ, researchers found that 258 subjects with extremely low birth weights (less than 1000 g) had Wechsler IQ scores at age 8 with a mean of 95.5 and a standard deviation of

### Confidence Intervals for Number of Unpopped Popcorn Kernels

Biting an unpopped kernel of popcorn hurts! As an experiment, a self-confessed connoisseur 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 p

### A sample of 20 pages was taken without replacement from the 1,591-page phone directory Ameritech Pages Plus 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

### 97% and 90% Confidence Intervals

Survey of 60 showed the sample mean is 2.76 and the standard deviation is 0.75. Construct a confidence interval of 90 and 97% for the population mean.

### (a) Use Chebyshev's theorem to find what percent of the values will fall between 120 and 150 for a data set with mean of 135 and standard deviation of 7.5.

(a) Use Chebyshev's theorem to find what percent of the values will fall between 120 and 150 for a data set with mean of 135 and standard deviation of 7.5. (b) Use the Empirical Rule to find what two values 95% of the data will fall between for a data set with mean 234 and standard deviation of 12.

### Confidence interval for apples per tree

A study of 200 apples trees showed that the average number of apples per tree was 1000. The standard deviation of the population is 200. Which of the following is the 98% confidence interval for the mean number for all apples. a. (967.1, 1032.9) b. (963.8, 1036.2) c. (963.6, 1036.4) d. (972.3, 1027.7)

### A recent poll of 700 people who worked indoors found that 278 of them smoke.

A recent poll of 700 people who worked indoors found that 278 of them smoke. If the researchers want to be 98% confident of thier results to within 3.5 %, how large a sample is necessary. a. 1062 b. 532 c. 751 d. 1301

### The 90% confidence interval of the true proportion

It was found that in a sample of 90 teenage boys, 70 % of them have received speeding tickets. What is the 90% confidence interval of the true proportion of teenage boys who have received speeding tickets? a. 0.591 < p < 0.812 b. 0.615 < p < 0.805 c. 0.620 < p < 0.780 d. 0.584 < p < 0.830

### What is the 95% confidence interval for the standard deviation of birth weights at County General Hospital

What is the 95% confidence interval for the standard deviation of birth weights at County General Hospital, if the standard deviation of the last 25 babies born there was 1.1 pounds. a. 0.7 < o < 2.3 b. 0.9 < o < 1.5 c. 0.8 < o < 2.1 d. 0.8 < o < 1.9

### Confidence Interval for the Mean Weight per White Mice

A study of 80 white mice showed that their average weight was 3.7 ounces. The standard deviation of the population is 0.6 ounces. What is the 95% confidence interval for the mean weight per white mice?

### Probability , hypothesis testing and confidence interval for a set of problems.

I would like help with the following exercises for future reference and a better overall understanding. Thanks! 1. The Los Angeles sheriff classifies crimes by age (in years) of the criminal and whether the crime is violent or nonviolent. As shown below, the sheriff reported a total of 150 crimes last year. Age (in years)

### Confidence interval for proportion problem

Please help with the following problems involving confidence intervals. 1. Find the point estimate p-hat and the margin of error for the confidence interval (0.444, 0.484) 2 With destructive testing, sample items are destroyed in the process of testing them. Crash testing of cars is one very expensive example of destruct

### Confidence interval for mean

Please see attached. If you can help me with the details of the nine attached questions...with detailed formulas and solutions, I really would appreciate it. 1. Of 139 adults selected randomly from one town, 30 of them smoke. a. Construct a 99% confidence interval for the true percentage of all adults in the town that

### Estimation of the Population Proportion or Mean

Please see attached worksheet. If you can give me detailed formulas with answers it would be great. 1. The local Tupperware dealers earned these commissions last month: \$4377.47 \$3183.76 \$1970.16 \$2270.88 \$3860.06 \$2508.55 \$1569.64 \$4205.30 \$1663.68 \$3960.71 Assuming the population for the amount of commissions ea

### The manager of the Inlet Square Mall, just north of Ft. Meyers

The manager of the Inlet Square Mall, just north of Ft. Meyers, Florida, wants to estimate the mean amount spent per shopping visit by customers. A sample of 20 customers reveals the following amounts spent: (Data in the excel file). What is the best estimate of the population mean? Determine a 95 percent confidence interval.

### Finding the Confidence Interval

1. Find the 90 percent confidence interval for the standard deviation of gasoline mileage mpg for these 16 San Francisco commuters driving hybrid gas-electric vehicles. 38.8 48.9 28.5 40.0 38.8 29.2 29.1 38.5 34.4 46.1 51.8 30.7 36.9 25.6 42.7 38.3 2. Biting an un-popped kernel of popcorn hurts! As an experiment, a self

### Confidence interval for mean and proportion..

Let's assume that the family size factor for the class was collected from randomly selected students taking Elements of Statistics from FHSU?even though we know the data was not randomly collected from such students. a. First, determine from this sample data the proportion (percentage) of students from families of si

### Determine P (AUB) , given that A and B are mutually exclusive. What is the probability that a randomly selected finance major is female. What is the probability that the student is both a freshman and a mathematics major? For each of the variables described below, indicate whether the variable is a quantitative or a categorical (qualitative) variable. Find a 99% confidence interval for the true mean of all scores. Find a 90% confidence interval for the mean daily return on this stock. What is the probability that exactly 2 of the workers interviewed are union members? Find the probability that the disposal of such capacitors will be regulated.

1. Suppose that A and B are independent events such that P (A bar) = 0.50 and P (B) = 0.70. Find P ( A intersection B) and P (AUB) . 2. Let A and B be two events such that P(A)= 0.20 and P(B) = 0.05. . (a) Determine P (AUB) , given that A and B are mutually exclusive . (b) Determine P (A

### A random sample of 10 miniature Tootsie Rolls was taken from a bag. Each piece was weighed on a very accurate scale. (a) Construct a 90 percent confidence interval for the true mean weight.

8.46 A random sample of 10 miniature Tootsie Rolls was taken from a bag. Each piece was weighed on a very accurate scale. The results in grams were 3.087, 3.131, 3.241, 3.241, 3.270, 3.353, 3.400, 3.411, 3.437, 3.477 (a) Construct a 90 percent confidence interval for the true mean weight. (b) What sample size would be necessar

### Sample size and confidence interval

(21) The U.S. Commission of Crime wishes to estimate the fraction of crimes related to firearms in an area with one of the highest crime rates in the country. The commission randomly selects 600 files of recently committed crimes in an area and finds 380 in which a firearm was reportedly used. Construct the 95% confidence interv

### Confidence Interval for the population mean

The lifetime of a certain brand of electric light bulb is known to have a standard deviation of 49 hours. Suppose that a random sample of 50 bulbs of this brand has a mean lifetime of 491 hours. Find a 95% confidence interval for the true mean lifetime of all light bulbs of this brand. Then complete the table below. Carry yo

### Confidence Interval for Population Mean: T-Distribution

A random sample of 18 health maintenance organizations(HMOs) was selected. For each HMO, the co-payment(in dollars for a doctor's office visit was recorded. The results are as follows: 6, 12, 7,7,11,9,5,10,12,9,11,12,8,8,5,7,5,8. See the attached file for further details. Under the assumption that co-payment amounts are

### Find a confidence interval for mean assuming that each sample is from a normal population.

Find a confidence interval for mean assuming that each sample is from a normal population. a. ¯x = 24, s = 3, n = 7, 90 percent confidence b. ¯x = 42, s = 6, n = 18, 99 percent confidence c. ¯x = 119, s = 14, n = 28, 95 percent confidence

### Confidence interval using Normal Distribution. Find the 95 percent confidence interval for the mean score on each exam. Do the confidence intervals overlap?

Prof. Hardtack gave three exams last semester in a large lecture class. The standard deviation s = 7 was the same on all three exams, and scores were normally distributed. Below are scores for 10 randomly chosen students on each exam. Find the 95 percent confidence interval for the mean score on each exam. Do the confidence inte

### A food inspector, examining 5 jars of a certain brand of peanut butter, obtained the following percentages of impurities

1) A food inspector, examining 5 jars of a certain brand of peanut butter, obtained the following percentages of impurities: 2.3; 1.9; 2.1; 2.8; 2.3 Assuming that such determinations are normally distributed, construct a 99% confidence interval for the average percentage of impurities in this brand of peanut butter. 2)

### Step by step method for testing the hypothesis under 5 step approach is discussed here. The solution also include the details of sampling distribution of the samples from a normal population.

1.When you draw a sample from a normal distribution, what can you conclude about the sample distribution? Explain. 2.A mayoral election race is tightly contested. In a random sample of 1,100 likely voters, 572 said that they were planning to vote for the current mayor. Based on this sample, what is your initial hunch? Would y

### Find the sample size needed for a 95% degree of confidence.

The weekly earnings of middle managers in a large corporation are approximately normally distributed with a standard deviation of 36 dollars. A researcher wishes to estimate the mean weekly earnings. Find the sample size needed if she requires a 95% degree of confidence that the sample mean will not differ from the population by