An experiment was planned to compare the mean time (in days)required to recover from a...

In a study on the effect of an oral rinse on plaque buildup on teeth, fourteen...

In a study on the effect of an oral rinse on plaque buildup on teeth, fourteen people whose teeth were thoroughly cleaned and polished were randomly assigned to two groups of seven subjects each. Both groups were assigned to use oral rinses (no brushing) for a 2-week period. Group 1 used a rinse that contained an antiplaque agent. Group 2, the control group, received a similar rinse except that the rinse contained no antiplaque agent. A measure of plaque buildup...

An article in American Demographics investigated consumer habits at the mall. We tend to spend the...

An article in American Demographics investigated consumer habits at the mall. We tend to spend the most money shopping on the weekends, and, in particular, on Sundays from 4 to 6 p.m. Wednesday morning shoppers spend the least! Suppose that a random sample of 21 weekend shoppers and a random sample of 21 weekday shoppers were selected, and the amount spent per trip to the mall was recorded. Weekends Weekdays Sample Size 21 21 Sample Mean ($) 75 62 Sample...

Shear strength measurements derived from unconfined compression tests for two types of soil gave the results...

Shear strength measurements derived from unconfined compression tests for two types of soil gave the results shown in the following table (measurements in tons per square foot). Soil Type I Soil Type II n1 = 30 n2 = 35 y1 = 1.69 y2 = 1.46 s1 = 0.24 s2 = 0.22 Do the soils appear to differ with respect to average shear strength, at the 1% significance level? State the null and alternative hypotheses. H0: μ1 = μ2 Ha: μ1...

A fruit grower wants to test a new spray that a manufacturer claims will reduce the...

A fruit grower wants to test a new spray that a manufacturer claims will reduce the loss due to insect damage. To test the claim, the grower sprays 200 trees with the new spray and 200 other trees with the standard spray. The following data were recorded.      New Spray     Standard Spray Mean Yield per Tree (lb)     240 228 Variance s2 980 807 (a) Do the data provide sufficient evidence to conclude that the mean yield per tree treated with...

A random sample of 37 second graders who participated in sports had manual dexterity scores with...

A random sample of 37 second graders who participated in sports had manual dexterity scores with mean 32.29 and standard deviation 4.14. An independent sample of 37 second graders who did not participate in sports had manual dexterity scores with mean 31.88 and standard deviation 4.86. (a) Test to see whether sufficient evidence exists to indicate that second graders who participate in sports have a higher mean dexterity score. Use α = 0.05. State the null and alternative hypotheses. (Us...

A sample of 57 observations is selected from one population with a population standard deviation of...

A sample of 57 observations is selected from one population with a population standard deviation of 0.73. The sample mean is 2.62. A sample of 54 observations is selected from a second population with a population standard deviation of 0.64. The sample mean is 2.5. Conduct the following test of hypothesis using the 0.1 significance level: H0: μ1 – μ2 ≤ 0 H1: μ1 – μ2 > 0 a. Is this a one-tailed or a two-tailed test? This is a...

A random sample of n1 = 14 winter days in Denver gave a sample mean pollution...

A random sample of n1 = 14 winter days in Denver gave a sample mean pollution index x1 = 43. Previous studies show that σ1 = 21. For Englewood (a suburb of Denver), a random sample of n2 = 12 winter days gave a sample mean pollution index of x2 = 37. Previous studies show that σ2 = 17. Assume the pollution index is normally distributed in both Englewood and Denver. (a) Do these data indicate that the mean population...

An experiment was conducted to test the effect of a new drug on a viral infection....

An experiment was conducted to test the effect of a new drug on a viral infection. After the infection was induced in 100 mice, the mice were randomly split into two groups of 50. The first group, the control group, received no treatment for the infection, and the second group received the drug. After a 30-day period, the proportions of survivors, p?1 and p?2, in the two groups were found to be 0.38 and 0.66, respectively. (a) Is there sufficient...

A sample of 65 observations is selected from one population with a population standard deviation of...

A sample of 65 observations is selected from one population with a population standard deviation of 0.78. The sample mean is 2.69. A sample of 54 observations is selected from a second population with a population standard deviation of 0.69. The sample mean is 2.57. Conduct the following test of hypothesis using the 0.1 significance level: H0: μ1 – μ2≤ 0 H1: μ1 – μ2 > 0 a. Is this a one-tailed or a two-tailed test? This is a ___...

A sample of 66 observations is selected from one population with a population standard deviation of...

A sample of 66 observations is selected from one population with a population standard deviation of 0.68. The sample mean is 2.67. A sample of 45 observations is selected from a second population with a population standard deviation of 0.68. The sample mean is 2.59. Conduct the following test of hypothesis using the 0.1 significance level: H0: μ1 – μ2≤ 0 H1: μ1 – μ2 > 0 a. Is this a one-tailed or a two-tailed test? This is a  (Click to...