ores, is the of o = 10. After a treatment is administered to the that the treat- individuals in the sample, the sample mean is found to a two-tailed test be M = 46. a. How large a sample is necessary for this sample es, is the sample mean to be statistically significant? Assume a two- treatment has tailed test with a = .05. d test with . If the sample mean were M = 43, what sample size is needed to be significant for a two-tailed test with and b, explain a = .05? es the outcome 14. Researchers at a National Weather Center in the northeastern United States recorded the number of elected from 90 Fahrenheit days each year since records first 50. After started in 1875. The numbers form a normal-shaped iduals in the distribution with a mean of u. = 9.6 and a standard M = 54. deviation of o = 1.9. To see if the data showed any is o = 8, is the evidence of global warming, they also computed the that the treat- mean number of 90 days for the most recent two-tailed test n = 4 years and obtained M = 12.25. Do the data indicate that the past four years have had signifi- is o = 12, is cantly more 90 days than would be expected for a de that the random sample from this population? Use a one- se a two-tailed tailed test with a = .05. 15. A high school teacher has designed a new course and b, explain deviation influ- intended to help students prepare for the mathemat- ics section of the SAT. A sample of n = 20 students est. ited for the cour the end of the year