# Hypothesis Testing- Everything You Must Know in 2023

In today's data-driven world, data is often used to make informed decisions. When it comes to making business decisions, hypotheses are a crucial aspect of that process. Without hypotheses and hypothesis testing, you are at risk of drawing the wrong conclusions and making the wrong decisions. In their daily tasks, data scientists make a lot of predictions, and they perform hypothesis testing to determine the likelihood that a conclusion is true or false. The main purpose of hypothesis testing is to evaluate the performance of the predictions using the population sample data. Let us walk through the various types of hypothesis testing that help data scientists come up with the right judgments and make better decisions. ### 1. Null Hypothesis

A null hypothesis is a specific type of statistical hypothesis that asserts that no statistical significance can be found in a given set of observations. The testing is considered null hypothesis testing if the data given at the beginning does not correspond with the outcomes. It is represented as H0 and is often referred to as simply the "null." Let's say a research is conducted to determine whether girls are shorter than boys at age 5. The null hypothesis states that they are of equal height.

### 2. Alternative Hypothesis

The alternative hypothesis identifies and explains how two variables are related. It just denotes a positive correlation between two variables, proving that they are statistically related. It implies that the outcome will be influenced by or affected by the sample that was observed. Ha represents an alternative hypothesis, and H1 describes the probability of an influenced outcome, which is 1. For instance, "there was no change in the water level this spring" may be the null hypothesis, while "there was a change in the water level this spring" could be the alternative hypothesis.

### 3. Directional (One-Tailed) Hypothesis

A directional hypothesis is a hypothesis that is based on an existing theory and a specific directional relationship between two variables. The test sample must be higher than or lower than a given value for the crucial distribution area to be one-sided in a one-tailed test. Here is an example to help you better understand what a directional hypothesis is: Girls perform better than boys (the word "better" indicates the intended direction).

### 4. Non-directional (Two-Tailed) Hypothesis

A non-directional (two-tailed) hypothesis assumes that the independent variable will influence the dependent variable, but does not specify which direction the effect will flow. There will be a difference between the two groups/conditions, but it doesn't specify whether that difference will be bigger or smaller, occur faster or slower, etc. For instance, if you say that "those who revise a lot and those who do not revise have different exam scores," then this hypothesis is non-directional.

### 5. Statistical Hypothesis

A statistical hypothesis is a hypothesis that relates to the parameters or form of the probability distribution for a certain population or populations, or, more generally, of a probabilistic mechanism that is supposed to yield the observations. It is an excellent way of determining whether the values and data that you now have support the stated hypothesis or not. It helps you in generating various probabilistic and conclusive statements about the outcome of the population. T-tests, Z-tests, and Anova tests are various types of statistical hypothesis testing.

Being a data scientist requires gaining the right skills and knowledge of specific subjects, statistics being one of them. So, keep learning and upskilling yourself! 