# Null and Alternative Hypotheses for a Mean

Typically in a hypothesis test, the claim being made is about a population (one number that characterizes the entire population). Because parameters tend to be unknown quantities, everyone wants to make claims about what their values may be. For example, the claim that 25% (or 0.25) of all women have varicose veins is a claim about the proportion (that’s the ) of all women (that’s the ) who have varicose veins (that’s the — having or not having varicose veins).

## Try out a range of class widths, and choose the one that works best.

### Another party proposes an alternative hypothesis.

**A regression model for situations in which** values of the response variable may not be sampled at random from the population of interest. For example, if the response variable is salary and the population women, it may be that women who would have low wages choose not to work and so the sample of observed salaries is biased upwards.

### First, you have to choose a significance level .

Finally, say you work for the company marketing the pie, and you think the pie can be made in less than five minutes (and could be marketed by the company as such). The less-than alternative is the one you want, and your two hypotheses would be

## define null alternative hypothesis: ..

On the other hand, the null hypothesis is straightforward -- what is the probability that our treated and untreated samples are from the same population (that the treatment or predictor has no effect)? There is only one set of statistical probabilities -- calculation of chance effects. Instead of directly testing H, we test H. If we can reject H, (and factors are under control), we can accept H. To put it another way, the fate of the research hypothesis depends upon what happens to H.

## Null and alternative hypothesis definition

John Watson = Father of Behaviorism

Albert and the Rabbit

He went to work in advertising industry as many psychologists did.

## null and alternative hypothesis ..

The statistical analysis will allow you to reject either the null or the alternative hypothesis. If the alternative is rejected, then you need to go back and refine the initial hypothesis or design a completely new research program.