A quiz question gives random samples of n = 10 observations from each of two Normally distributed populations. Tom uses a table of t distribution critical values and 9 degrees of freedom to calculate a 95% confidence interval for the difference in the two population means. Janelle uses her calculators two-sample t interval with 16.87 degrees of freedom to compute the 95% confidence interval. Assume that both students calculate the intervals correctly. Which of the following is true? (a) Toms confidence interval is wider. (b) Janelles confidence interval is wider. (c) Both confidence intervals are the same. (d) There is insufficient information to determine which confidence interval is wider. (e) Janelle made a mistake; degrees of freedom has to be a whole number

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 sample information to make conclusions about a larger group of items/individuals than just those in the sample. - Population: The entire group of items/individuals that we want information about, about which inferences are to be made. - Sample: The smaller group, the part of the population we actually e