L12 - One and Two sample T-tests Flashcards
What does hypothesis testing do?
it is used to test the validity of a claim (AKA the Null Hypothesis) that is about population using sample data.
what is a P-value
it is a measure of how surprising it is that the null hypothesis gets rejected as a probability.
- The lower the p-value, the more surprising the evidence is.
what does a one sample t-test do?
It is a statistical hypothesis test used to determine whether an unknown population mean is different from a specified value.
what are the required assumptions for a one sample t-test 2
- The data are interval or ratio
- The sample is drawn from a population that is normally distributed.
What are the two things that you are comparing within a one sample t-test.
one will be the calculated t value from a data set. The other could be the population parameter, or a performance expectation.
What is the equation for a one sample t-test
T = sample mean - comparison value
__________________________________
Standard error of the mean
what is a sampling distribution?
The distribution of values taken by a statistic when one takes all possible samples of a given size from a population, and graph it
what is the equation for the standard error of the mean
SE = s / n^-1
What is the standard error of the mean?
It is the standard deviation of the sampling distribution.
whats the difference between standard deviation and standard error of the mean?
the standard error of the mean estimates the variability between samples whereas the standard deviation measures the variability within a single sample.
what does alpha represent?
significance level
what does DF represent?
Degrees of freedom (n-1)
what are three ways to test normality?
- histogram and box-plot
- normal probability plot
- goodness of fit test
Draw positively skewed distribution, negatively skewed distribution and a bimodal distribution.
positively skewed - majority of data points closer to 0
negatively skewed - majority of points further away from zero
Bimodel - has two peaks in the dataset.
what two variables are needed to find the critical value of T
Degrees of freedom and the significance level