The birth weights for two groups of babies were compared in a study. In one group the mothers took a zinc supplement during pregnancy. In another group, the mothers took a placebo. A sample of 165 babies in the zinc group had a mean birth weight of 3402 grams. A sample of 127 babies in the placebo group had a mean birth weight of 3027 grams. Assume the standard deviation is known to be 723 grams for the population of babies whose mothers took a zinc supplement during pregnancy and 791 grams for babies whose mothers did not. Determine the 98 % confidence interval for the true difference between the mean birth weights for "zinc" babies versus "placebo" babies. Step 1 of 2: Find the critical value that should be used in constructing the confidence interval.

A researcher claims that the stomachs of blue crabs from Location A contain more fish than the stomachs of blue crabs from Location B. The stomach contents of a sample of 16 blue crabs from Location A contain a mean of 192 milligrams of fish and a standard deviation of 37 milligrams. The stomach contents of a sample of 11 blue crabs from Location B contain a mean of 189 milligrams of fish and a standard deviation of 45 milligrams. At α=0.01​, can you support the​ researcher's claim? Assume the population variances are equal. Complete parts​ (a) through​ (d) below.

A regional airline serving Las Vegas has a base airfare rate of $99. In addition, various fees are charged: for checked baggage, refreshments/drinks in-flight, and for making a reservation on its website. These additional charges average $70 per passenger. Suppose a random sample of 59 passengers is taken to determine the total cost of their flight. The population standard deviation of total flight cost is known to be $40. (a) What is the population mean cost per flight in dollars? $  (b) What is the probability the sample mean will be within $10 of the population mean cost per flight? (Round your answer to four decimal places.)   (c) What is the probability the sample mean will be within $5 of the population mean cost per flight? (Round your answer to four decimal places.)

The heights of 10 year old American children are normally distributed with a mean height of 4 feet and 5 inches (or 53 inches) and a standard deviation of 4.5 inches.In order to be allowed to go on a particular kids ride at the amusement park, children must be at least 44.9 inches tall and no more than 59.75 inches tall.What percent of 10 year old American children cannot go on the ride?

A car company claims that its new SUV gets better gas mileage than its competitor's SUV. A random sample of 49 of its SUVs has a mean gas mileage of 17.1 miles per gallon (mpg). The population standard deviation is known to be 1.3 mpg. A random sample of 33 competitor's SUVS has a mean gas mileage of 16.3 mpg. The population standard deviation for the competitor is known to be 1.6 mpg. Test the company's claim at the 0.05 level of significance. Let the car company be Population 1 and let the competitor be Population 2. Step 2 of 3: Compute the value of the test statistic. Round your answer to two decimal places.

In a certain country the heights of adult men are normally distributed with a mean of 67.2 inches and a standard deviation of 2.3 inches. The​ country's military requires that men have heights between 64 inches and 75 inches. Determine what percentage of this​ country's men are eligible for the military based on height.

A local church parish wants to raise money to add to their campus. In a sample from a previous fund raising campaign, the parish found that of the 131 people in the sample they contacted, that 69 actually contributed money. Of those that contributed money, the average contribution was $857 with a standard deviation of $265. In the recent fundraising campaign, a sample of 95 people revealed that 48 have contributed money with an average contribution of $1109 and a standard deviation of $339. When testing (at the 5% level of significance) whether the average amount contributed has increased in the current campaign compared to the previous campaign, what is the test statistic? (please round your answer to 2 decimal places)

The birth weights for two groups of babies were compared in a study. In one group the mothers took a zinc supplement during pregnancy. In another group, the mothers took a placebo. A sample of 176 babies in the zinc group had a mean birth weight of 3270 grams. A sample of 220 babies in the placebo group had a mean birth weight of 3144 grams. Assume that the population standard deviation for the zinc group is 718 grams, while the population standard deviation for the placebo group is 780 grams. Determine the 90%90% confidence interval for the true difference between the mean birth weights for "zinc" babies versus "placebo" babies.   Find the point estimate for the true difference between the population means.

In one city, the average amount of time that tenth-graders spend watching television each week is 23 hours. The principal of Birchwood High School believes it is less for the 10th grade students that at his school.  For a sample of 95 tenth-graders from the school, the mean amount of time spent watching television per week was 21.9 hours.  Assuming a population standard deviation of 3.1 hours, does the data provide sufficient evidence to conclude that for all tenth-graders at Birchwood High school, the mean amount of time spent watching television per week is less than the city average of 23 hours?  Perform the appropriate hypothesis test using a significance level of 0.005.  What are the hypotheses?         What is the test statistic? Is it a z or a t?         Find the P-value for this test statistic. How does it compare to the significance level?  On the normal curve, indicate the location of the test statistic  and  the p-value. (label them on the graph)                 Write…

Steve believes that his wife's cell phone battery does not last as long as his cell phone battery. On eight different occasions, he measured the length of time his cell phone battery lasted and calculated that the mean was 19.7 hours with a standard deviation of 9.4 hours. He measured the length of time his wife's cell phone battery lasted on twelve different occasions and calculated a mean of 18.9 hours with a standard deviation of 5.3 hours. Assume that the population variances are the same. Let Population 1 be the battery life of Steve's cell phone and Population 2 be the battery life of his wife's cell phone. Step 1 of 2: Construct a 90 % confidence interval for the true difference in mean battery life between Steve's cell phone and his wife's. Round the endpoints of the interval to one decimal place, if necessary.