Statistical Test Purposes Flashcards
What do statistical tests provide?
provides a mechanism for making quantitative decisions about a process or processes
What’s a p value
estimates how likely it is that you would see the difference described by the test statistic if the null hypothesis of no relationship were true.
When ton perform a statistic test?
You can perform statistical tests on data that have been collected in a statistically valid manner – either through an experiment, or through observations made using probability sampling methods.
When is a stat tets valid?
sample size needs to be large enough to approximate the true distribution of the population being studied.
To determine which statistical test to use, you need to know:
whether your data meets certain assumptions.
the types of variables that you’re dealing with.
Homogeneity of variance:
the variance within each group being compared is similar among all groups. If one group has much more variation than others, it will limit the test’s effectiveness.
Normality of data:
the data follows a normal distribution (a.k.a. a bell curve). This assumption applies only to quantitative data.
Independence of observations ( no autocorrelation):
The observations/variables you include in your test are not related (for example, multiple measurements of a single test subject are not independent, while measurements of multiple different test subjects are independent).
Non parametric stat test is used when ..
If your data do not meet the assumptions of normality or homogeneity of variance, you may be able to perform a nonparametric statistical test,
What does a non parametric test allow you to make ?
which allows you to make comparisons without any assumptions about the data distribution.
What if my data didn’t meet assumptions of independence of observations?
you may be able to use a test that accounts for structure in your data (repeated-measures tests or tests that include blocking variables).
Types of quantitative variables include:
Continuous (aka ratio variables)
Discrete (aka integer variables)
Types of categorical variables include:
Ordinal
Nominal
Binary
Correlation tests check …
whether variables are related without hypothesizing a cause-and-effect relationship.
Repeated measures / within groups
Subjects are measured 2 or more times on the dependent variable
