When T-test assumptions aren't met Flashcards
Data distributions: What is a positive skew?
Skewed to the right - mean is to the right of the median
like a right foot
Data distributions: What is a negative skew?
Skewed to the left - mean is the left of the median
What is positive/right skew bounded by?
Data is bounded by zero
What is negative/left skew bounded by?
Data is bounded by the maximum value
What is kurtosis?
It measures tail extremity, by representing the presence of outliers in a distribution
The larger the number (+ve or -ve) the less normally distributed the data
Positive and negative kurtosis
if a dataset has a positive kurtosis, it has more in the tails than the normal distribution
negative kurtosis means that your distribution is flatter than a normal curve with the same mean and standard deviation
Use of Mann-Whitney U test
If data is continuous
Mann-Whitney U test compares the sum of ranks
Mann-Whitney U test is used to compare whether there is a difference in the dependent variable for two independent groups.
What is Levene’s test used for?
When performing a t-test, Levene’s test for equality of variance of data between
groups
Levene’s test tests for equal variance between samples