30. Other Things to Consider - Impact of Large Sample Size

One of the most important aspects of interpreting any statistical results (and one that is frequently overlooked) is assuring that your sample is truly representative of your population of interest.

Particularly in the way that data is collected today in the age of computers, response bias is so important to keep in mind. In the 2016 U.S election, polls conducted by many news media suggested a staggering difference from the reality of poll results. You can read about how response bias played a role here .

Hypothesis Testing vs. Machine Learning

With large sample sizes, hypothesis testing leads to even the smallest of findings as statistically significant . However, these findings might not be practically significant at all.

For example, imagine you find that statistically more people prefer beverage 1 to beverage 2 in a study of more than one million people. Based on this you decide to open a shop to sell beverage 1. You then find out that beverage 1 is only more popular than beverage 2 by 0.0002% (but a statistically significant amount with your large sample size). Practically, maybe you should have opened a store that sold both.

Hypothesis testing takes an aggregate approach towards the conclusions made based on data, as these tests are aimed at understanding population parameters (which are aggregate population values).

Alternatively, machine learning techniques take an individual approach towards making conclusions, as they attempt to predict an outcome for each specific data point.

In the final lessons of this class, you will learn about two of the most fundamental machine learning approaches used in practice: linear and logistic regression.