2, 3, 4a, 4b

2. An English professor counted the number of misspelt words in an essay he recently assigned. For the class of 240 students, the mean number of misspelled words was 6.05 and the standard deviation of 2.44. Construct a 95% confidence interval for the mean number of misspelled words in the population of students. 3. An IQ test was given to a sample of 75 students at a certain college. The sample mean score was 105.2. Scores on this test are known to have a standard deviation of 10. Construct a 95% confidence interval for the mean IQ score. 4. According to the National Health Statistics Reports, a sample of 360 one-year baby boys in the USA had a mean weight of 25.5 pounds. Assume the population standard deviation is 5.3 pounds. a) Construct a 95% confidence interval for the mean weight of all one-year old baby boys. b) Is it likely that the mean weight is less than 28 pounds