An engineer designed a valve that will regulate water pressure on an automobile engine. The engineer designed the valve such that it would produce a mean pressure of 4.34.3 pounds/square inch. It is believed that the valve performs above the specifications. The valve was tested on 280280 engines and the mean pressure was 4.44.4 pounds/square inch. Assume the variance is known to be 0.640.64. A level of significance of 0.050.05 will be used. Make a decision to reject or fail to reject the null hypothesis.    Make a decision.

Air Quality Index is a way to measure particle pollution in the air. An index between 0 and 50 is considered good; between 51 and 100 is moderate; more 100 is considered unhealthy for sensitive groups and others. A recent sample data of air quality index values for Pomona in Southern California provided the following data. 50, 52, 59, 56, 58 What are the sample mean, sample variance and the sample standard deviation?

Suppose a researcher is interested in a new treatment plan for increasing CD4 cell count in immune-compromised patients with HIV. In order to investigate the new drug, the researcher gathers a group of 48 individuals with a mean CD4 count of 317 cells/mm3 after treatment with a standard deviation of 24.6. Test the hypothesis that the mean CD4 count has increased above the goal of 275 cells/mm3. Write out your hypotheses and correctly interpret your pvalue. (Use an alpha level of 0.01)

High-power experimental engines are being developed by the Stevens Motor Company for use in its new sports coupe. The engineers have calculated the maximum horsepower for the engine to be 830HP . Twenty five engines are randomly selected for horsepower testing. The sample has an average maximum HP of 820 with a standard deviation of 80HP . Assume the population is normally distributed. Step 1 of 2 :  Calculate a confidence interval for the average maximum HP for the experimental engine. Use a significance level of α=0.1 . Round your answers to two decimal places.

The primary difference(s) between the standard deviation and the coefficient of variation as measures of risk are:

A recent article in a business journal reported that the mean annual salary for graduates from 30 top MBA programs           10 years after graduation is  $275,000 Assume the standard deviation is $54,500 24 Keep the error probability at α = 0.05.  We want to build an interval which captures 95% of the sample means within ±$5,000 from the population mean.  What is the minimum sample size that would yield such an interval?                                     a 411                 b 457                 c 508                 d 564

The nutrition label for Oriental Spice Sauce states that one package of sauce has 1030 milligrams of sodium. To determine if the label is accurate, the FDA randomly selects 130 packages of Oriental Spice Sauce and determines the sodium content. The sample has an average of 1000.15 milligrams of sodium per package with a sample standard deviation of 271.69 milligrams. Step 1 of 2 : Calculate a 95% confidence interval for the mean sodium content in Oriental Spice Sauce. Round your answers to two decimal places.

A cereal company checks the weight of its breakfast cereal by randomly checking 62 of the boxes. This particular brand is packed in 20-ounce boxes. Suppose that a particular random sample of 62 boxes results in a mean weight of 20.04 ounces. How often will the sample mean be this high, or higher if u = 20 and σ = 0.10 4