An automobile company is looking for fueladditives that might increase gas mileage. Without additives, theircars are known to average 18 mpg (miles pergallons) with a standard deviation of 3 mpg on a road trip from Muscat to Sur. The company now asks whethera new additive increases this value. In a study, forty cars are sent on a road trip from Muscat to Sur. Şuppose it turns out that the forty cars averaged = (18.75) mpg with the additive. Can we conclude from this result that the additive is effective? a. With a significance level of 5%. b. With a significance level of 1%.

The population of weights of a particular fruit is normally distributed, with a mean of 248 grams and a standard deviation of 26 grams. If 11 fruits are picked at random, then 3% of the time,  their mean weight will be greater than how many grams? Round to the nearest gram.

A researcher speculates that because of differences in diet, Japanese children have a lower mean blood cholesterol level than U.S. children do. Suppose that the mean level for U.S. children is known to be 165. Let μ represent the true mean blood cholesterol level for Japanese children. What hypotheses should the researcher test? Ho: μ = 165 versus H₂: μ> 165 a O Ho: μ = 165 versus H₂: μ 165 O Ho: μ = 165 versus H: μ > 155

A particular fruit's weights are normally distributed, with a mean of 271 grams and a standard deviation of 28 grams.If you pick 3 fruits at random, then 7% of the time, their mean weight will be greater than how many grams?Give your answer to the nearest gram.

A particular fruit's weights are normally distributed, with a mean of 317 grams and a standard deviation of 29 grams. If you pick 25 fruits at random, then 5% of the time, their mean weight will be greater than how many grams? Give your answer to the nearest gram.

A particular fruit's weights are normally distributed, with a mean of 689 grams and a standard deviation of 13 grams.If you pick 10 fruits at random, then 4% of the time, their mean weight will be greater than how many grams?Give your answer to the nearest gram.

In Professor Krugman’s economics course, the correlation between the students’ total scores prior to the final examination and their final‑examination scores is ?=0.5.r=0.5. The pre‑exam totals for all students in the course have mean 280280 and standard deviation 40.40. The final‑exam scores have mean 7575 and standard deviation 8.8. Professor Krugman has lost Julie’s final exam but knows that her total before the exam was 300.300. He decides to predict her final‑exam score from her pre‑exam total. (a) Which of the choices is the least‑squares regression line of final‑exam scores on pre‑exam total scores in this course?

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 =

It takes an average of 14.5 minutes for blood to begin clotting after an injury. An EMT wants to see if the average will increase if the patient is immediately told the truth about the injury. The EMT randomly selected 70 injured patients to immediately tell the truth about the injury and noticed that they averaged 16.3 minutes for their blood to begin clotting after their injury. Their standard deviation was 4.75 minutes. What can be concluded at the the α = 0.10 level of significance? a. For this study, we should use [Select an answer b. The null and alternative hypotheses would be: Ho: ? Select an answer H₁: ? Select an answer ✓ c. The test statistic ? = (please show your answer to 3 decimal places.) d. The p-value = (Please show your answer to 4 decimal places.) e. The p-value is ? ✓ a f. Based on this, we should [Select an answer the null hypothesis. g. Thus, the final conclusion is that ... O The data suggest the populaton mean is significantly greater than 14.5 at a = 0.10, so…

The level of calcium in the blood of healthy young adults follows a normal distribution with mean u = 10 milligrams per deciliter and standard deviation s = 0.4.  A clinic measures the blood calcium of 100 healthy pregnant young women at their first visit for prenatal care.  The sample mean of these 100 measurements is  X = 9.8.  Is this evidence that the mean calcium level in the population from which these women come is less than 10?  To answer this question, we perform the following hypothesis test: H0: u = 10, Ha: u < 10. What is the test statistic? (use two decimal places in your answer) What is the p-value equal to? At the 10% significance level, do you accept or reject the null hypothesis? Answer ACCEPT or REJECT t the 5% significance level, do you accept or reject the null hypothesis? Answer ACCEPT or REJECT