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education/statistics/Hypothesis Tests.md
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@ -49,10 +49,21 @@ Degrees of freedom ($df$) can be found by subtracting 1 from the sample size. Th
The equivalent of $normalcdf$ for a t test is $tcdf$. This function returns a percentage. The equivalent of $normalcdf$ for a t test is $tcdf$. This function returns a percentage.
## P Value ## P Value
The chance of observing at least a sample statistic, or something more extreme, if the null hypothesis is true. The *chance of observing at least a sample statistic, or something more extreme*, if the null hypothesis is true.
If the **p-value is less than *5*%, reject the null** hypothesis, evidence. If the **p-value is less than *5*%, reject the null** hypothesis, evidence.
If the **p-value is greater than *5*%, fail to reject** the null hypothesis, not enough evidence. If the **p-value is greater than *5*%, fail to reject** the null hypothesis, not enough evidence.
Investigators should:
- Summarize the data
- Say what test was used
- Report the p-value
Investigators should not:
- Blindly compare P to 5% or 1%, there are real world factors that change how important this value is.
### Data Mining/Snooping
(Ch 28-29, stat 1040) (Ch 28-29, stat 1040)
## Goodness of fit tests ($\chi ^2$) ## Goodness of fit tests ($\chi ^2$)
This test is used when you have one qualitative variable with many categories, eg the (color, size, shape) of an (item). This test is used when you have one qualitative variable with many categories, eg the (color, size, shape) of an (item).