How many four-letter code words are possible using the letters in IOWA if (a) The letters may not be repeated? (b) The letters may be repeated?

Lecture 3: Sampling: Surveys and How to Ask Questions 5.1 Collecting and Using Sample Data Wisely Definitions: - Descriptive Statistics: Describing data using numerical summaries (such as the mean, IQR, etc.) and graphical summaries (such as histograms, bar charts, etc.). - Inferential Statistics: Using...