Practice Problems #9 - Applied Statistics for Engineers and Scientists | STAT 541, Assignments of Statistics

Download Practice Problems #9 - Applied Statistics for Engineers and Scientists | STAT 541 and more Assignments Statistics in PDF only on Docsity!

Practice Problems # 09

1. In a test of the effect of dampness on electric connections, 100 electric connections were tested under damp conditions and 150 were tested under dry conditions. Twenty of the damp condition connections failed and only 10 of the dry condition connections failed. a. Test the hypothesis that the two proportions are equal versus the hypothesis that they are not equal. Use α = 0.10 and perform the 8 steps for testing hypotheses. b. Find the p-value of this test of hypothesis. c. Find a 90% confidence interval on the difference of the two proportions.
2. A study in which eight types of white wine reports the tartaric acid concentration (in g/L) measured before and after a cold stabilization process. The results are presented in the following table. Wine Type Before After 1 2.86 2. 2 2.85 2. 3 1.84 1. 4 1.60 1. 5 0.80 0. 6 0.89 0. 7 2.03 1. 8 1.90 1.

Find a 95% confidence interval for the difference of the means for the tartaric concentrations before and after the cold stabilization process. Assume that the measurements of tartaric concentrations follow a normal distribution.

3. Two sets of data yielded the following statistics: s 12 = 2.3 based on a sample of size 6, and s 22 = 0.6 with a sample of size 10. Find a 99% confidence interval on the ratio of the

standard deviations, σ 1 σ 2.

4. An experiment was performed to determine whether the annealing temperature of ductile iron affects its tensile strength. Five specimens were annealed at each of four temperatures. The tensile strength (in ksi) was measured for each. The partially complete ANOVA table for this problem is as follows:

Source df

Sums of Squares

Mean Squares Temp Error 2. Total 95.

a. Complete the ANOVA table. b. What is the value of the F statistic for H 0 : μ 1 = μ 2 = μ 3 = μ 4 vs. Ha: at least one mean is different from the others? c. What is the p-value for this test?