Researchers know that the distribution of the number of eggs in a robin's nest is normally distributed, but are concerned that the mean number of eggs per nest of robin's eggs has decreased from the mean of 4.8 eggs measured 10 years ago. They send out teams to locate and randomly select 20 nests and count the number of eggs in each nest. The team calculated a mean of 4.5 and a standard deviation of 0.7 eggs per nest. Is there evidence at the 0.05 significance level that the mean number of eggs per robin's nest has decreased over the past 10 years?

A parenting magazine reports that the average amount of wireless data used by teenagers each month is 5 Gb. For her science fair project, Ella sets out to prove the magazine wrong. She claims that the mean among teenagers in her area is less than reported. Ella collects information from a simple random sample of 25 teenagers at her high school, and calculates a mean of 4.7 Gb per month with a standard deviation of 0.9 Gb per month. Assume that the population distribution is approximately normal. Test Ella's claim at the 0.01 level of significance. Step 3 of 3: Draw a conclusion and interpret the decision. E Tables E Keypad Answer Keyboard Shortcuts We reject the null hypothesis and conclude that there is sufficient evidence at a 0.01 level of significance that the average amount of wireless data used by teenagers each month is less than 5 Gb. We fail to reject the null hypothesis and conclude that there is insufficient evidence at a 0.01 level of significance that the average amount of…

The combined SAT scores for the students at a local high school are normally distributed with a mean of 1469 and a standard deviation of 296. The local college includes a minimum score of 1824 in its admission requirements. What percentage of students from this school earn scores that satisfy the admission requirement?

According to Current Population Reports, the population distribution of number of years of education for self-employed individuals in the United States has a mean of 13.6 and a standard deviation of 3.0.  Find the mean and standard error of the sampling distribution of ȳ for a random sample of  9 residents.

The combined SAT scores for the students at a local high school are normally distributed with a mean of 1478 and a standard deviation of 292. The local college includes a minimum score of 689.6 in its admission requirements.What percentage of students from this school earn scores that satisfy the admission requirement?

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.

According to the Bureau of Labor Statistics, the mean salary for registered nurses in Kentucky was $55,130. The distribution of salaries is assumed to be normally distributed with a standard deviation of $5,778. Someone would like to determine if registered nurses in Ohio have a greater average pay. To investigate this claim, a sample of 220 registered nurses is selected from the Ohio Board of Nursing, and each is asked their annual salary. The mean salary for this sample of 220 nurses is found to be $55,504.488.  Completely describe the sampling distribution of the sample mean salary when samples of size 220 are selected. mean:  μ x-bar = ____ standard deviation: σ x-bar  = ____ shape: the distribution of is ____________(not normally distributed/normally distributed) because ___________ (the sample size is large/the sample size is not large/the population of salaries is normally distributed/the population of salaries is not normally distributed)

A parenting magazine reports that the average amount of wireless data used by teenagers each month is 10 Gb. For her science fair project, Ella sets out to prove the magazine wrong. She claims that the mean among teenagers in her area is less than reported. Ella collects information from a simple random sample of 16 teenagers at her high school, and calculates a mean of 9.1 Gb per month with a standard deviation of 1.3 Gb per month. Assume that the population distribution is approximately normal. Test Ella's claim at the 0.05 level of significance. Step 3 of 3: Draw a conclusion and interpret the decision.

According to the Bureau of Labor Statistics, the mean salary for registered nurses in Kentucky was $57,688. The distribution of salaries is assumed to be normally distributed with a standard deviation of $5,879. Someone would like to determine if registered nurses in Ohio have a greater average pay. To investigate this claim, a sample of 192 registered nurses is selected from the Ohio Board of Nursing, and each is asked their annual salary. The mean salary for this sample of 192 nurses is found to be $58,016.005.  1. Completely describe the sampling distribution of the sample mean salary when samples of size 192 are selected. 2. What conjecture has been made? 3. Using the distribution described in part a, what is the probability of observing a sample mean of 58,016.005 or more? 4. Based on the probability found, what conclusion can be reached?