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A study of the influence of corrosion inhibitor on the failure of aluminum-wired twist-on connections, the data obtained with one sample of connectors wired with alloy aluminum and another sample wi
A study found that the average time it took a person to find a new job was 3.5 months. If a sample of 30 job seekers was surveyed, find the 90% confidence interval of the mean. Assume the standard d
A survey found that Americans generate an average of 19.8 pounds of glass garbage each year. Assume the standard deviation of the distribution is 2.9 pounds. Find the probability that the mean of a
What is the total number of African American died from heart disease if they represent 13% of the 316,000,000 American population?
A company has 1,300 items. In a sample of 120 items, the historical cost of each item was compared with the audited value, and 10 items differed in their historical costs and audit values. Construct
A researcher wishes to estimate the percentage of adults who support abolishing the penny. What size sample should be obtained if he wishes the estimate to be within 2 percentage points with 90% con
Construct a 95% confidence interval estimate of the total value of the merchandise in inventory at the end of the month.
A survey is planned to determine the mean annual family medical expenses of employees of a large company. The management of the company wishes to be 90% confident that the sample mean is correct to
The proportion of all children that drew the nickel too small is: 38/75. Assume that this proportion is true for ALL children (e.g. that this proportion applies to any group of children),
A plant purifies its liquid waste and discharges the water into a local river. The EPA collects water specimens of the discharge of the plant and also water specimens in the river upstream from the
If np> and nq>5, estimate P(more than 4) with n=12 and p=0.7 by using the normal distribution as an approximation to the binomial distribution to the binomial; if np<5 or nq<5, then stat
Every year sixth-grade students in Ohio schools take proficiency tests. The list of sixth-grade reading score changes from the prior year are given below.
Construct a C chart for the number of unsafe acts. Based on the results of (a), is the process in a state of statistical control? What should management do next to improve the process?
With a Mean of 2.0 seconds and Standard Deviation of 0.5
In late 2007, it was reported that 79% of U.S. adults owned a cell phone (data extracted from E.C. Baig, "Tips Help Navigate Tech-Buying Maze", USA Today, November 28, 200, p.5B). Suppose that by th
Whites represent 77.7% of the USA and 38.8% is on welfare, Blacks represent 13.2 % of the USA and 39.8% is on welfare, And Hispanics represent 17% of the USA and 15.7% is on welfare. There's 316 mil
You are unconvinced and are trying to calculate the significance p-value for the null hypothesis: that the support stays on the level 50%. You use normal approximation. What is this p?
Make sure you clearly state both the null and the alternative hypotheses in full sentences. Include the output table; then clearly state the conclusion in the same manner (do not simply say "accept/
A group of investors wants to develop a chain of fast-food restaurants. In determining potential costs for each facility, they must consider, among other expenses, the average monthly electric bill.
The mean weight on my sons football team is 185 pounds with a standard deviation of 20 pounds. Determine the standard z-score and the percentile for the data below:
It is known that the lifetime of a lightbulb is normally distributed with a mean lifetime of 1,060 hrs and a standard deviation of 125 hrs. What is the probability that a randomly selected light bul
An unfair coin comes up heads 38% of the time. If the coin is flipped 12 times, what is the probability that it comes up heads no more than two times?
List some of the risks in using samples to make inferences about populations from which the samples were drawn. What can be done to mitigate these risks?
Give two suggestions regarding how a statistician might generate probability estimates when empirical data is unavailable.
Would experimental effects (such as Hawthorne effects) be a problem in this program? If so, how? Alternatively, what threats to internal validity might exist in this program?