IN THIS CHAPTER
Understanding estimation statistics
Using the Student’s t-distribution test functions
Analyzing probabilities and results with the chi square functions
When you have data from a population, you can draw a sample and run your statistical analysis on the sample. You can also run the analysis on the population itself. Is the mean of the sample data the same as the mean of the whole population? You can calculate the mean of both the sample and the population and then know precisely how well the sample represents the population. Are the two means exact? Off a little bit? How much different?
The problem with this, though, is that getting the data of the entire population in the first place isn’t always feasible. On average, how many miles per gallon does a Toyota Camry get after 5 years on the road? You cannot answer this question to an exact degree, because it’s impossible to test every Camry out there.
Instead, you infer the answer. Testing a handful, or sample, of Camrys is certainly possible. Then the mean gas mileage of the sample is used to represent the mean gas mileage of all 5-year-old Camrys. The mean of the sample group will ...