1. What is the most controllable method of increasing the precision (narrowing) of the confidence interval? 2. What percentage of times will the mean (population proportion) not be found within the confidence interval? 3. When you draw a sample from a normal distribution, what can you conclude about the sample distribution? Ex
3. A sample of 49 households is taken from a population in which the standard deviation is 7. The standard error of the mean isPlease see the attached file. 4. It is desired to construct a 95% confidence interval. The correct value of Z to obtain for the 95% confidence interval is: ... 5. A confidence interval has been const
A dean of a business school wanted to know whether the graduates of her school used a statistical inference technique during their first year of employment after graduation. She surveyed 314 graduates and asked about the use of statistical techniques. After tallying up the responses, she found that 204 used statistical inference
Assume that the random variable is normally distributed A parking control officer is conducting an analysis of the amount of time left on parking meters. A quick survey of 15 cars that have left their metered parking spaces produced the following times (in minutes). Estimate with 95% confidence the mean amount of time left f
A statistics professor wants to compare today's students with those from 25 years ago. All of his current students' marks are stored on a computer so that he can easily determine the population mean. However, the marks from 25 years ago reside only in his paper files. He does not want to retrieve the marks and will be satisfie
The operations manager of a large production plant would like to estimate the average amount of time workers take to assemble a new electronic component. After observing a number of workers assembling similar devices, she guessed that the standard deviation is 6 minutes. How large a sample of workers should she take if she wis
The following observations are the ages of a random sample of 8 men in a bar. It is known that the ages are normally distributed with a standard deviation of 10. Determine the 95% confidence interval estimate of the population mean. Interpret the interval estimate. 52 68 22 35 30 56 39 48
Never forget that even small effects can be statistically significant if the samples are large. Of 148 small businesses, 106 were headed by men and 42 were headed by women. During a three-year period, 15 of the men's businesses and 7 of the women's businesses failed. a) Find the proportions of failures for businesses headed
What percentage of times will the mean (population proportion) not be found within the confidence interval? What is the most controllable method of increasing the precision (narrowing) of the confidence interval?
(A) 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
A manufacturer would like to estimate the average number of copies that can be made from a single bottle of toner. A random sample of 20 bottles was selected for this experiment. For the 20 bottles of toner the average number of pages was 1535 with a standard deviation of 50 pages. a) Compute the 95% confidence interval f
A sample of n=16 scores is obtained from an unknown population. The sample has a mean of M=46 with SS=6000. a. Use the sample data to make an 80% confidence interval estimate of the unknown population mean. b. Make a 90% confidence interval estimate of μ. c. Make a 95% confidence interval estimate of μ.
A random sample of 28 observations from a normally distributed population produced a mean x( bar over x = 24.2 and a standard deviation s =2.56. Find 95% confidence intervals for the population mean.
Please show all steps and send the solution in an attachment. please 1. A random sample of 80 observations from a normally distributed population produced a mean x(bar over the x)= 22.6 . Find a 95% confidence interval for the population mean m if the population standard deviation o(looks like a small o with a tip this sign
Use the given confidence level and sample data to find a confidence interval for estimating the population mean m 1. salaries of college graduates who took a statistics course in college : 95% confidence; n=41, x(bar over x) = $67,200, and o( omega or sigma )is known to be $18, 277.
Problem: Calculate the margin of error E = zomega /2omega is exponent square root of n if the necessary requirements are satisfied . If the requirements are not satisfied , state that the margin of error cannot be calculated by using this methods of this section 1. The confidence level is 95%, the sample size is n=100
In 1992, the FAA conducted 86,991 pre-employment drug test on job applicants who were to be engaged in safety and security-related jobs, and found that 1,143 were positive. A)Construct a 95% confidence interval for the population proportion of positive drug tests. B)Why is the normality assumption not a problem, despite the very
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% confidence interval for the true mean weight. b)What sample size would be necessary to estimate the
A bolt manufacturer grabs 5 bolts from his production line and measures them. The results are 102mm, 101mm, 101mm, 95mm, and 106mm. What is the lower bound for the 95% confidence interval for the mean bolt length?
What do we mean by mean, variance and confidence interval?
A machine for making nuts is known to create nuts with a standard deviation in size of 0.20mm. A tradesman is required to adjust the machine to make 49mm nuts. Unfortunately the machines scale is missing and the tradesman has to adjust it by trial and error. How many nuts does he have to make and test after an adjustment before
50. Use the following information to construct the confidence intervals specified to estimate µ a) 95% confidence; = 25, σ2 = 12.25, and n = 60. b) 98% confidence; = 119.6, S2 = 570.7321, and n = 75. c) 90% confidence; ∑X = 1814.4, σ2 = 0.948676, and n = 32. 51. A sample of size n = 10 is randomly sel
1. A random sample of 500 measurements on the length of stay in hospitals had sample mean 5.4 days and sample standard deviation 3.1 days. A federal regulatory agency hypothesizes that the average length of stay is in excess of 5 days. a. Do the data support this hypothesis? Use  = 0.05. b. Construct a 98% confiden
A random sample taken of 1200 likely voters a week before election show that 628 of them plan on voting for Abraham Washington in the upcoming election. Calculate a 95% confidence interval and a 90% confidence interval based on this data. Then state this interval in a single sentence, explaining to Mr. Washington his chances o
1. a) A random sample of 100 managers in Alaska had an average yearly income of $125,500 with a standard deviation of $20,000. Develop the 95%, 90%, and 99% confidence intervals for the yearly income of all managers in Alaska. b) If we assume we know the standard deviation of yearly income of all managers in Alaska is $25,00
A sampling of a lot of soybean meal gave the following composition for Lysine in (grams/kilogram): 22.2 24.8 24.7 26.5 20.9 23.8 26.0 25.6 27.0 23.9 Do the following: a) Construct a 99% two sided confidence interval for (std. deviation)^2. b) Calculate a 99% lower confidence bound for (std deviation)^2. c) Calc
An article in Medicine and Science in Sports titled "Maximal Leg Strength Training" studied cycling performance before and after 8 weeks of training. Seven cyclists trained for 8 weeks; peak power increased to mean of 315 watt with a standard deviation of 16 watts. Construct a 95% confidence interval for the mean peak power a
The life in hours of a 75 watt light bulb is known to be normally distributed with std deviation of 25 hours. A random sample of 20 bulbs has a mean life of 1014 hours. a) Construct a 95% two sided confidence interval on the mean life. b) Construct a 95% lower-confidence bound on the mean life. Compare the lower bound o
Jennifer wants to find a 95% confidence interval for the time it takes her to get to work. She kept records for 30 days and found her average time to commute to work was 20.5 minutes with a standard deviation of 3.9 minutes. What is Jennifer's maximum error of estimate in minutes?
A food snack manufacturer samples 7 bags of pretzels off the assembly line and weighed their contents. If the sample mean is 10.4 and the sample standard deviation is 0.15, find the 95% confidence interval of the true mean.