Choosing a statistical test. Flashcards
What is a quantitative variable?
Numbers which mean something in the real world.
Continuous // Discrete variables.
What is a categorical variable?
Numbers which assign participants to groups.
Nominal // Ordinal variables.
What is the difference between paired and unpaired data?
Paired means there is some natural link between 2 observations whereas with independent this means the probability of A occurring DOES NOT influence the probability of B occurring.
What is a t - test used for?
Used to test the difference between the means.
What is the purpose of ( independent ) two sample t tests?
Compare the means between 2 independent groups.
What is the purpose of ( paired ) two sample t tests?
Compare the means of the same measurement made at 2 different time points in one group.
What is the purpose of one sample t - test?
Compares the mean of sample with estimated population mean.
What is the H0 for a t - test?
There is NO difference in the continuous variable between groups (independent) or time points (paired).
What is the H1 for a t - test?
There is A difference in the continuous variable between groups (independent) or time points (paired).
What happens if the p - value is <0.05?
You reject the null hypothesis : there IS a difference in the continuous variable between groups.
What are the assumptions for a t - test?
Data is RANDOMLY sampled from the population of interest.
Variable = One categorical variable which has 2 group (independent) or timepoints (paired) AND one continuous dependent variable.
What is a chi - squared test?
Calculates the chi - square statistic by comparing the observed value to the expected value.
How do you calculate the degrees of freedom?
(r-1) * (c-1)
What are the assumptions for a chi - square test?
Data is frequencies // counts
Study groups are independent and each participant contributes data to only one cell.
Value of cell EXPECTED should be >5 in >80% of cells and NOT zero.
In chi square, what does the null hypothesis (H0) show?
Categories are INDEPENDENT // NOT RELATED
In chi square, what does the alternate hypothesis (H1) show?
Categories are NOT INDEPENDENT // ARE RELATED
What is the correlation coefficient?
Describes the strength and direction of the LINEAR relationship between 2 CONTINUOUS variables.
What does p and r stand for in correlation coefficients?
P = population parameter r = sample statistic
What are the assumptions for Pearson’s correlation?
2 continuous variables which are paired.
Normal distribution = NO OUTLIERS.
Relationship is LINEAR.
What does homoscedasticity mean?
Shape of scatter plot is tube - like NOT cone shape.
