9. The Taylor Steel Company wants to determine whether there is a significant difference in productivity between day-shift workers and night-shift workers. A random sample of 130 day-sh workers shows a mean output of 66.3 parts per hour with a standard deviation of 14.0 parts per hour, while a random sample of 120 night-shift workers shows a mean output of 62.7 parts per hour with a standard deviation of 16.0 parts per hour. a. Is there evidence in these results of a difference in productivity between day-shift and nigl shift workers? Use a 5% significance level. (Do not assume that the two population standard deviations are equal. Show all four steps of your hypothesis test.) b. Calculate a 95% confidence interval for the difference between the group means. What does this confidence interval imply about whether you can reject the null hypothesis of no difference in productivity between the two shifts? Is this result consistent with the result of your t-test of the difference in means in part a? Explain why it is (or isn’t).

A national business magazine reports that the mean age of retirement for women executives is 61.5. A women’s rights organization believes that this value does not accurately depict the current trend in retirement. To test this, the group polled a simple random sample of 91 recently retired women executives and found that they had a mean age of retirement of 62.0. Assuming the population standard deviation is 2.5 years, is there sufficient evidence to support the organization’s belief at the 0.10 level of significance?   Step 2 of 3 :   Compute the value of the test statistic. Round your answer to two decimal places.

Suppose that water usages in American showers are normally distributed, with an average shower using 20 gallons, and a standard deviation of 3.2 gallons. Estimate the percentage of showers that used (a) between 13.6 and 26.4 gallons. % (b) more than 26.4 gallons. % (c) less than 10.4 gallons. % (d) between 16.8 and 29.6 gallons. %

A marketing researcher wants to estimate the mean amount spent per year ($) on a web site by membership member shoppers. Suppose a random sample of 100 membership member shoppers who recently made a purchase on the web site yielded a mean amount spent of $55 and a standard deviation of $52. Complete parts (a) and (b) below. a. Is there evidence that the population mean amount spent per year on the web site by membership member shoppers is different from $51? (Use a 0.01 level of significance.) State the null and alternative hypotheses. Ho: H (Type integers or decimals. Do not round. Do not include the $ symbol in your answer.) Identify the critical value(s). The critical value(s) is/are (Type an integer or a decimal. Round to two decimal places as needed. Use a comma to separate answers as needed.) Determine the test statistic. The test statistic, 1STAT, is (Type an integer or a decimal. Round to two decimal places as needed.) State the conclusion. Ho. There is evidence that the…

Fran is training for her first marathon, and she wants to know if there is a significant difference between the mean number of miles run each week by group runners and individual runners who are training for marathons. She interviews 42 randomly selected people who train in groups and finds that they run a mean of 47.1 miles per week. Assume that the population standard deviation for group runners is known to be 4.4 miles per week. She also interviews a random sample of 47 people who train on their own and finds that they run a mean of 48.5 miles per week. Assume that the population standard deviation for people who run by themselves is 1.8 miles per week. Test the claim at the 0.01 level of significance. Let group runners training for marathons be Population 1 and let individual runners training for marathons be Population 2.   Step 2 of 3 :   Compute the value of the test statistic. Round your answer to two decimal places.

3. Netflix: A study conducted in 2015 by the technology company Rovi (now TiVo) showed that the mean time spent per day browsing the video streaming service Netflix for something to watch was 19.3 minutes. Assume the standard deviation is o = 8. Suppose a simple random sample of 100 visits taken this year has a sample mean of 21.5 minutes. A social scientist is interested to know whether the mean time browsing Netflix has increased. Test the scientist's claim using a 0.05 significance level. 1. List the null and alternate hypothesis. 2. List the distribution (z or t) and all given variables used. 3. Find the critical value(s) using your calculator and label the picture. Draw a picture!!

A marketing researcher wants to estimate the mean amount spent per year​ ($) on a web site by membership member shoppers. Suppose a random sample of 100 membership member shoppers who recently made a purchase on the web site yielded a mean amount spent of ​$58and a standard deviation of ​$55.Complete parts​ (a) and​ (b) below. a. Is there evidence that the population mean amount spent per year on the web site by membership member shoppers is different from ​$51​? ​(Use a 0.01 level of​ significance.)   State the null and alternative hypotheses.

Suppose that on a certain section of I-95, with a posted speed limit of 65 miles per hour, the speeds of all vehicles have a bell-shaped distribution with a mean of 72 mph and a standard deviation of 3 mph. Find the percentage of vehicles with the following speeds on this section of I-95: greater than 75 mph. Use the Empirical Rule. Suppose that on a certain section of I-95, with a posted speed limit of 65 miles per hour, the speeds of all vehicles have a bell-shaped distribution with a mean of 72 mph and a standard deviation of 3 mph. Find the percentage of vehicles with the following speeds on this section of I-95: greater than 75 mph. Use the Empirical Rule. 81.5% 16% 32% 34% 50%

1) A​ half-century ago, the mean height of women in a particular country in their 20s was 63.7 inches. Assume that the heights of today's women in their 20s are approximately normally distributed with a standard deviation of 2.31 inches. If the mean height today is the same as that of a​ half-century ago, what percentage of all samples of 26 of today's women in their 20s have mean heights of at least 65.04 ​inches?

A national business magazine reports that the mean age of retirement for women executives is 63.7. A women’s rights organization believes that this value does not accurately depict the current trend in retirement. To test this, the group polled a simple random sample of 93 recently retired women executives and found that they had a mean age of retirement of 63.0. Assuming the population standard deviation is 3.0 years, is there sufficient evidence to support the organization’s belief at the 0.05 level of significance?   Step 3 of 3 : Draw a conclusion and interpret the decision.   1. We fail to reject the null hypothesis and conclude that there is suffiecient evidence at a 0.05 level of significance to support the belief that the mean age of retirement for women executives is not 63.7.   2. We reject the null hypothesis and conclude that there is suffiecient evidence at a 0.05 level of significance to support the belief that the mean age of retirement for women executives is not…