Professor Smith took a sample of 210 students from her morning class and a sample of 163 students from her evening class. On Exam 1, all those sampled from the morning class got a 67 while those sampled from the evening class averaged a 67 with a variance of 127. If Professor Smith combines these two samples.What is the combined Exam 1 Average?What is the combined Exam 1 median?What is the combined Exam 1 Standard Deviation?

Here are 6 celebrities with some of the highest net worths (in millions of dollars) in a recent year: Oprah Winfrey (3200), Michael Jordan (1700), Paul McCartney (1200), J. K. Rowling (1000), David Copperfield (1000), and Jerry Seinfeld (950). Find the range, variance, and standard deviation for the sample data. What do the results tell us about the population of all celebrities? Based on the nature of the amounts, what can be inferred about their precision? The range is $ million. (Round to the nearest integer as needed.) ...

In a standardized exam the mean score is 400 with a standard deviation of 50. If a random sample of 25 students is selected , what is the standard deviation of the sampling distribution of the sample mean ?

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 37 randomly selected people who train in groups, and finds that they run a mean of 47.7 miles per week. Assume that the population standard deviation for group runners is known to be 3.3 miles per week. She also interviews a random sample of 49 people who train on their own and finds that they run a mean of 49.4 miles per week. Assume that the population standard deviation for people who run by themselves is 4.4 miles per week. Test the claim at the 0.10 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.

Suppose Professor Alpha and Professor Omega each teach Introductory Biology. You need to decide which professor to take the class from and have just completed your Introductory Statistics course. Records obtained from past students indicate that students in Professor Alpha's class have a mean score of 80% with a standard deviation of 5%, while past students in Professor Omega's Class have a mean score of 80% with a standard deviation of 10%. Decide which instructor to take for Introductory Biology using a statistical argument.

For her test grades, Gena has a mean = 65 and standard deviation = 25. Patti has a mean = 65 and standard deviation = 5.   For which of the students can you more accurately predict the next test score, and why? Consider the variability of scores.   Who is more likely to do either extremely well or extremely poorly on the next exam, and why?   Explain the reason for adjusting the formula of the standard deviation/variance with n - 1 in the denominator?

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.

Researchers want to compare the relative effectiveness of two popular diets. They randomly assign each of 400 volunteers to one of two Groups: A & B.  There are 200 volunteers in each group. Group A spends 6 months on Diet A. Group B spends 6 months on Diet B.   At the beginning of the study, the difference in average weight between the two groups was negligible. After the study, the Group A had lost on average 7.8 pounds with a standard deviation of 13.4 pounds, while the Group B had lost on average 5.3 pounds with a standard deviation of 14.8 pounds. Determine the z-score/test statistic for a two-tailed test with significance level α = 0.05 , accurate to 2 decimal places.

What is the equation for The standard deviation of the distribution of sample means

Professor Hayashi has implemented a new book for his Fall 2013 statistics course. He wants to see if the new book has an effect on the exam average for Exam 3. He knows that the Exam 3 mean for all students who have taken his statistic course over the past 10 years is 77.2. He collects some data from a sample of 9 students and finds that the Exam 3 mean for his Fall 2013 statistics students is 81.7 with a variance of 32.49.Measure effect size using percentage of variance