A Case Study
We have a problem.
In our lab, we found a huge amount of similar robots on a planet (physical population). To know more about the weight of these robots (statistical population), we first need to choose some of them (physical sample), then obtain the weight of them (statistical sample).
To describe the data, we could calculate the mean of the weight. We found that the mean weight is 93kg (descriptive statistics).
How can we know the mean weight of this kind of robot? We know the mean weight of those robot that we selected. We need a link to the actual mean weight of all the robots on the planet (inferential statistics, estimation).
In the end, we will have a conclusion of the mean weight of all the robots on the planet. Then again, how could we be sure that our conclusion is correct (hypothesis testing)?