2. A team of eye surgeons has developed a new technique for eye operation to restore the sight of people. Under the old method, it is known that only 30% of the patients who undergo this operation recover their eyesight. Suppose that surgeons have performed n = 225 operations using the new method and that x = 88 have been successful. Can we justify the claim that the population proportion is different from 30% ? Use a a=0.01. (Hint: use the Normal Distribution)

A sample of N = 9 individuals participates in a repeated measures study that produces a sample mean difference of X = 4.25 with SS = 128 for the difference scores. Is this mean difference large enough to be considered a real positive effect?

There are many situations in which we want to compare means from populations having standard deviations that are equal. This method applies even if the standard deviations are known to be only approximately equal. Consider a report regarding average incidence of fox rabies in two regions. For region I, n1 = 16, x1 ≈ 4.73, and s1 = 2.84 and for region II, n2 = 15, x2 ≈ 3.93, and s2 = 2.45. The two sample standard deviations are sufficiently close that we can assume ?1 = ?2. Use the method of pooled standard deviation to consider the report, testing if there is a difference in population mean average incidence of rabies at the 5% level of significance. (Round your answer to three decimal places.) t =

Imagine that a researcher wants to compare the intelligence levels of Poodles to all dogs.  He hypothesizes that Poodles will score differently than other dogs.  He uses a standard test of dog intelligence in his study. The population of all dogs has a mean of μ = 100, and an SD of 15.  He obtains a random sample of 500 Poodles and he finds that the mean intelligence score of the sample is 117.   Is this a one- or two- tailed test? Write the Ho and Ha for this research question. What kind of statistic should be calculated to test the hypothesis? Compute that statistic by hand What should the researcher conclude? Write a blurb describing the results

Our environment is very sensitive to the amount of ozone in the upper atmosphere. The level of ozone normally found is 4.6 parts/million (ppm). A researcher believes that the current ozone level is at an excess level. The mean of 14 samples is 4.9 ppm with a variance of 1.2 Does the data support the claim at the 0.01 level? Assume the population distribution is approximately normal. Step 2 of 5 :   Find the value of the test statistic. Round your answer to three decimal places.

Child Health and Development Studies (CHDS) has been collecting data about expectant mothers in Oakland, CA since 1959. One of the measurements taken by CHDS is the weight increase (in pounds) for expectant mothers in the second trimester. In a fictitious study, suppose that CHDS finds the average weight increase in the second trimester is 14 pounds. Suppose also that, in 2015, a random sample of 40 expectant mothers have mean weight increase of 15.8 pounds in the second trimester, with a standard deviation of 6.2 pounds. A hypothesis test is done to see if there is evidence that weight increase in the second trimester is greater than 14 pounds. Find the p-value for the hypothesis test.  The p-value should be rounded to 4 decimal places.

Suppose an experiment finds that people taking a new herbal remedy get fewer colds than people taking a placebo.  The results are statistically significant at the 0.01 level.  Has the experiment proven that the herbal remedy works?

A researcher collected data from a sample of correctional officers and found that, on average, they made 47,173 dollars a year with S=6,364. Assuming that their salaries were normally distributed what proportion of correctional officers make less than 40,000 dollars a year?

Prices of diamonds are very sensitive to their weight (measured in carat). For example, the price of a 1 carat diamond tends to be much higher than the price of a 0.99 carats diamond. To study this phenomenon in more detail, we consider two random samples of diamonds, 0.99 carats and 1 carat, each sample of size 23. The average price of 0.99 carats diamonds in the sample is $4451, while the average price of 1 carat diamonds in the sample is $5681. From long-term studies, we know that both the prices of 0.99 carats diamonds and the prices of 1 carat diamonds are normally distributed with standard deviations oj = $1332 (0.99 carats) and o2 = $1613 (1 carat), respectively. (a) Carry out a hypothesis test at significance level 0.01 to evaluate whether the true average price µi of 0.99 carats diamonds is lower than the true average price µ2 of 1 carat diamonds. Specify Ho and Ha, the test statistic, and calculate the p-value or use p-value considerations to conclude. (b) Compute the type II…