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Download Four samples from a normal distribution (the same samples used in Worksheet 3)
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Worksheet #4 Working with normal data We go back to the simulated normal data in worksheet #3, and apply the various techniques we have been looking at. Data Statistics We have four samples of different size. We assume that they all come from a normal distribution (this Descriptive Statistics is important for estimating the variance). For each sample, compute Summaries only are given for convenience: • The sample mean • The sample variance Sample 1 • The sample standard deviation Count 100 Sum 229.930271898377 Estimating the mean Sum squares 546.063861553791 We did this already. If you want to try again, Sample 2 Count 50 Sum 114.735747991455 Sum squares 271.723417201116 Sample 3 Count 20 Sum 45.0531006969794 Sum squares 104.754650757329 Sample 4 Count 10 Sum 21.7571246035979 Sum squares 48.8597371544176 assume that the “true” standard deviation is 0.4 (this was the value used in the simulation) Estimating the variance Known mean Assume that the “true mean” (the expected value) is 2.3 – that is the value used in the simulation). Find a confidence interval for the variance at your chosen level for the four samples. Unknown mean Repeat the exercise without assuming any knowledge of the mean
