Tests of Independence and Correlation Flashcards
what is a independence test?
A statistical test used to analize the correlation between out samples.
when is the Chi-square Test used?
This test is used for analized independency between samples in a general way. It is the most frequently employed statistical technique for the analysis of count or frequency data.
How is the Chi-square test deined?
χ^2 =Σ(𝑂_i− 𝐸_i)^2 / 𝐸_i
Oi and Ei are observed and expected frequencies
What does a small p-value in a chi-square test indicate?
The variables are likely dependent
How are expected frequencies calculated in a chi-square test?
Using joint probabilities from the marginal totals. (the specic data/total subjectes )*the total group
What type of data is required for a chi-square test?
Frequency or count data.
When should Fisher’s exact test be used instead of a chi-square test?
For small sample sizes.
What does the correlation coefficient measure?
The strength and direction of a linear relationship between two variables. the degree of linear relationship between two variables.
What is the range of the correlation coefficient 𝑟?
From -1 to +1.
What does an 𝑟 value close to 0 imply?
Weak or no linear relationship. The closer the value of r to |1| is, the stronger the linear relationship
If the scatter plot is chaotic
What is the null hypothesis in a correlation test?
That the population correlation
𝜌 is 0.
What is the difference between Pearson’s and Spearman’s correlation?
Pearson measures linear relationships; Spearman measures rank-based relationships (For a non-parametric version of the correlation coefficient)
What does a positive correlation coefficient indicate?
As one variable increases, the other also increases. If all the points lie perfectly on a straight line and the line has a positive slope (the line slopes upward from left to right)
Beyond the topic: How might understanding correlations improve decision-making in healthcare?
open answer
How is the sample correlation denoted?
by the symbol r_xy or simply by r
The population correlation coefficient is denoted by ρ.
