The elasticity of a polymer is affected by the concentration of a reactant. Two random samples of size 20 are taken. When low concentration is used, the true mean elasticity is 56 and a standard deviation of elasticity is 4. Meanwhile, when high concentration is used the mean elasticity is 60 and a standard deviation of elasticity is 4. (a) Define the sampling distribution of (XHigh-XLow). (b) Find the probability that (XHigh-Low) ≥ 2.
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- A lot of 75 washers contains 6 defectives whose variability in thickness is unacceptably large. A sample of 10 washers is selected at random without replacement a. Find the probability that at least one unacceptable washer is in the sample b. Calculate the mean of (x) c. Calculate the standard deviation of (x)For each substance, estimate the standard deviation o by assuming uniform distribution and normal distribution shown in Table 8.11 in Section 8.8. (Round your answers to 4 decimal places.) Uniform Distribution Normal Distribution Chromium Barium FluorideA sample is selected from a population with A = 150. After a treatment is administered to the individuals, the sample mean is found to be = 140 and the standard deviation is S= 9. If the sample has n = 18 scores, determine whether the sample is sufficient to conclude that the treatment has significant effect. Use a two tail test with a = 0.02. (Assume the population is normally distributed)
- Steve, the underpaid graduate student, is interested in determining how many final grades in Dr. Boehring’sclass vary. Steve determines that the standard deviation of final grades in Dr. Tahkstumusch’s class is 7. Steve takes a random sample of 50 final grades from Dr. Boehring’s class and computes a standard deviation of 9.Assume that the final grades in Dr. Boehring’s class are normally distributed. At the 5% significance level, do the data provide sufficient evidence to conclude that the standard deviationσof final grades in Dr. Boehring’sclass are greater than 7? Use the rejection region approach for all of the parts below. (a) Define the appropriate hypotheses (b)State and verify that the proper assumptions hold (c)Use the rejection region approach to perform the test (d) Provide support for your decision regarding the null hypothesis (e) Write a summary of your conclusion in the context of the problemThe heights of fully grown trees of a specific species are normally distributed, with a mean of 71.0 feet and a standard deviation of 6.75 feet. Random samples of size 16 are drawn from the population. Use the central limit theorem to find the mean and standard error of the sampling distribution. Then sketch a graph of the sampling distribution. The mean of the sampling distribution is μx= The standard error of the sampling distribution is σx=A random sample of 25 night students was taken with a sample mean GPA of 2.86 and a standard deviation of 0.06. A random sample of 30 day students was taken with a sample mean GPA of 2.88 and a standard deviation of 0.07. Test the claim that the mean GPA of night students (μ) is different from the mean GPA of day students (μD) at a = 0.05. Assume that the data come from normal populations with unequal variances. Round your answers to three decimal places, and round any interim calculations to four decimal places. Fill in the hypotheses below (click the circle to the left of the correct answer): Ho: ên p σ΄ UN Td μD = v pО µÑ¯ ʵ¯Ñ¿© µD Ha: pOād up μι ên # PO μN X d This test is two-tailed. What is the test statistic? HD ên Part 2 of 4
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- A random sample of 10 observations from population A has sample mean of 152.3 and a sample standard deviation of 1.83. Another random sample of 8 observations from population B has a sample standard deviation of 1.94. Assuming equal variances in those two populations, a 99% confidence interval for μA − μB is (-0.19, 4.99), where μA is the mean in population A and μB is the mean in population B. (a) What is the sample mean of the observations from population B? (b) If we test H0 : μA ≤ μB against Ha : μA > μB, using α = 0.02, what is your conclusion?A sample is selected from a population with A = 150. After a treatment is administered to the individuals, the sample mean is found to be = 140 and the standard deviation is S= 9. If the sample has n = 18 scores, determine whether the sample is sufficient to conclude that the treatment has significant effect. Use a two tail test with a = 0.02. (Assume the population is normally distributed)Vehicle speeds at a certain highway location are believed to have approximately a normal distribution with mean µ = 50 mph and standard deviation σ = 5 mph. The speeds for a randomly selected sample of n = 25 vehicles will be recorded. (a) Give numerical values for the mean and standard deviation of the sampling distribution of possible sample means for randomly selected samples of n = 25 from the population of vehicle speeds. Mean = s.d.(x) = (b) Use the Empirical Rule to find values that fill in the blanks in the following sentence. For a random sample of n = 25 vehicles, there is about a 95% chance that the mean vehicle speed in the sample will be between and mph. (c) Sample speeds for a random sample of 25 vehicles are measured at this location, and the sample mean is 59 mph. Given the answer to part (b), explain whether this result is consistent with the belief that the mean speed at this location is μ = 50 mph. A sample mean of 59 mph (when n = 25) --Select--- be consistent with…