## Your hypothesis could be the following:

For our example, we formally state: The alternative hypothesis (H1) is that prenatal exposure to alcohol **has an effect** on the birth weight for the population of lab rats.

the opposite of the research hypothesis. The null hypothesis states that any effects observed after treatment (or associated with a predictor variable) are due to chance alone. Statistically, the question that is being answered is "If these samples came from the same population with regard to the outcome, how likely is the obtained result?"

## Below is a definition of the null hypothesis.

In statistics terminology, the students in the study are the **sample** and the larger group they represent (i.e., all statistics students on a graduate management degree) is called the **population**. Given that the sample of statistics students in the study are representative of a larger population of statistics students, you can use hypothesis testing to understand whether any differences or effects discovered in the study exist in the population. In layman's terms, hypothesis testing is used to establish whether a research hypothesis extends beyond those individuals examined in a single study.

## Example of a complex multiple independent variable hypothesis:

The (or hypothes*es* -- there may be more than one) is our working hypothesis -- our prediction, or what we expect to happen. It is also called the - because it is an alternative to the null hypothesis. Technically, the claim of the research hypothesis is that with respect to the outcome variable, our samples are from *different* populations (remember that refers to the group from which the sample is drawn). If we predict that math tutoring results in better performance, than we are predicting that after the treatment (tutoring), the treated sample truly is different from the untreated one (and therefore, from a different population).

## Example of a complex multiple dependent variable hypothesis:

The method will let us conclude whether (reject null hypothesis) or not (accept null hypothesis) the treatment (prenatal alcohol) has an effect (on birth weight).

## The significance level of a test. 4 Steps to Hypothesis Testing:

As such, by taking a hypothesis testing approach, Sarah and Mike want to **generalize** their results to a population rather than just the students in their sample. However, in order to use hypothesis testing, you need to re-state your research hypothesis as a null and alternative hypothesis. Before you can do this, it is best to consider the process/structure involved in hypothesis testing and what you are measuring. This structure is presented .

## The alternative hypothesis, a.k.a.

Generally, when comparing or contrasting groups (samples), the null hypothesis is that the *difference between means (averages) = 0*. For categorical data shown on a contingency table, the null hypothesis is that any differences between the observed frequencies (counts in categories) and expected frequencies are due to chance.

## The null hypothesis and the alternate hypothesis are ..

**Formally:** We **reject** the null hypothesis that prenatal exposure to alcohol **has no effect** on the birth weight for the population of lab rats.