T11.12 As a non-native English speaker, Sanda is convinced that people find more grammar and spelling mistakes in essays when they think the writer is a non- native English speaker. To test this, she randomly sorts a group of 60 volunteers into two groups of 30. Both groups are given the same paragraph to read. One group is told that the author of the paragraph is someone whose native language is not English. The other group is told nothing about the author. The subjects are asked to count the number of spelling and grammar mistakes in the paragraph. While the two groups found about the same number of real mistakes in the passage, the number of things that were incorrectly identified as mistakes was more interesting. Some numerical summaries of the data follow. Group n Mean SD Non-native 30 3.15 2.58 No info 30 0.85 1.09 a. Is there convincing evidence at the a - 0.05 significance level that the mean number of "mistakes" found will be greater when people like these volunteers are told that the author is a non-native speaker? b. Based on your conclusion in part (a), which type of error-a Type I error or a Type II error-could you have made? Explain your