Podcast
Questions and Answers
What does a correlation coefficient of -1.00 indicate?
What does a correlation coefficient of -1.00 indicate?
- Moderate positive correlation
- No correlation
- Perfect negative correlation (correct)
- Perfect positive correlation
Which test does not rely on the normality assumption?
Which test does not rely on the normality assumption?
- Spearman Rank Correlation
- Pearson Correlation Coefficient
- Simple Linear Regression
- Nonparametric tests (correct)
What does the Spearman Rank Correlation assess?
What does the Spearman Rank Correlation assess?
- Direction of relationship
- Strength and direction of a relationship
- Normality of data
- Independence of variables (correct)
In regression, what is the coefficient of determination (r^2) used for?
In regression, what is the coefficient of determination (r^2) used for?
What is a core assumption for Simple Linear Regression?
What is a core assumption for Simple Linear Regression?
When two variables move in opposite directions, this is known as:
When two variables move in opposite directions, this is known as:
Which statement about nonparametric tests is true?
Which statement about nonparametric tests is true?
What type of data is suitable for the Mann-Whitney U test?
What type of data is suitable for the Mann-Whitney U test?
In what situation would you use the Wilcoxon Signed-Rank Test?
In what situation would you use the Wilcoxon Signed-Rank Test?
When conducting the Kruskal-Wallis test, how many groups are being compared?
When conducting the Kruskal-Wallis test, how many groups are being compared?
What is a key assumption for the Chi-Square test?
What is a key assumption for the Chi-Square test?
Under what condition should Fisher's Exact test be used?
Under what condition should Fisher's Exact test be used?
Which test is suitable for comparing medians between two independent groups?
Which test is suitable for comparing medians between two independent groups?
What assumption is common between the Kruskal-Wallis and Mann-Whitney U tests?
What assumption is common between the Kruskal-Wallis and Mann-Whitney U tests?
Which correlation coefficient indicates the weakest relationship between two variables?
Which correlation coefficient indicates the weakest relationship between two variables?
What is the primary difference between Pearson and Spearman correlation coefficients?
What is the primary difference between Pearson and Spearman correlation coefficients?
Which of the following indicates the percentage of variance in the dependent variable that can be explained by the independent variable?
Which of the following indicates the percentage of variance in the dependent variable that can be explained by the independent variable?
What is a disadvantage of nonparametric tests compared to parametric tests?
What is a disadvantage of nonparametric tests compared to parametric tests?
Which of the following best describes the difference between correlation and regression?
Which of the following best describes the difference between correlation and regression?
Under which condition would simple linear regression be appropriate for analyzing a dataset?
Under which condition would simple linear regression be appropriate for analyzing a dataset?
Which of the following is an assumption of both Pearson and Spearman correlation coefficients?
Which of the following is an assumption of both Pearson and Spearman correlation coefficients?
What is a key difference between the Mann-Whitney U test and the Wilcoxon Signed-Rank Test?
What is a key difference between the Mann-Whitney U test and the Wilcoxon Signed-Rank Test?
What distinguishes Kruskal-Wallis test from Mann-Whitney U test?
What distinguishes Kruskal-Wallis test from Mann-Whitney U test?
Which assumption is unique to the Chi-Square test compared to other nonparametric tests?
Which assumption is unique to the Chi-Square test compared to other nonparametric tests?
When would you use Fisher's Exact test instead of the Chi-Square test?
When would you use Fisher's Exact test instead of the Chi-Square test?
What distinguishes the Wilcoxon Signed-Rank Test from the Mann-Whitney U test in terms of data requirements?
What distinguishes the Wilcoxon Signed-Rank Test from the Mann-Whitney U test in terms of data requirements?
What assumption differentiates the Kruskal-Wallis test from the Chi-Square test?
What assumption differentiates the Kruskal-Wallis test from the Chi-Square test?
What makes Fisher's Exact test unique compared to other nonparametric tests?
What makes Fisher's Exact test unique compared to other nonparametric tests?
What distinguishes the Wilcoxon Signed-Rank Test from the Kruskal-Wallis test in terms of their application?
What distinguishes the Wilcoxon Signed-Rank Test from the Kruskal-Wallis test in terms of their application?
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Study Notes
Correlation
- Evaluates the relationship between variables and direction of relationship
- Positively related: both move in the same direction
- Negatively related: move in opposite directions
- Correlation does not equal causation
- Correlation Coefficient: describes the strength and direction of a relationship, ranges from -1.00 to +1.00
- -1.00 = perfect negative correlation
- +1.00 = perfect positive correlation
Pearson Correlation Coefficient
- Assumptions: independence, normality, variables are interval/ratio level data
Spearman Rank Correlation
- Assumptions: independence
Regression
- Uses the relationship between variables as a basis for prediction
- Takes correlation a step further
- Simple Linear Regression: examines two variables that are linearly correlated
- Simple Linear Regression assumptions: normality, homogeneity of variances (Levene's test), and dependent variable is interval/ratio level data
- Regression Line formula: Y = a + bX
- Y = dependent variable
- a and b = constants
- X = independent variable
- r = correlation coefficient
- r2 = coefficient of determination (percentage of the variance in the dependent variable that can be explained by the independent variable)
Nonparametric Tests
- Do not rely on probability distribution (normality assumption)
- Do not have homogeneity of variances
- Can be used to examine nominal or ordinal level data
- Less powerful than parametric tests
Mann-Whitney U Test
- Evaluates whether medians differ significantly between two groups
- Assumptions: random samples, independence, and dependent variable is ordinal/interval/ratio level
Wilcoxon Signed-Rank Test
- Evaluates ranks for the difference between the measurements (use a before and after score and subtract to find rank)
- Cannot be used with ordinal data
- Assumptions: random samples and dependent variable is interval/ratio level
Kruskal-Wallis Test
- Evaluates whether medians differ significantly between 3+ groups
- Assumptions: random samples, independence, and dependent variable is ordinal/interval/ratio level data
Chi-Square Test
- Evaluates expected frequencies and observed frequencies of categorical (ordinal and nominal) data
- Assumptions: independence, expected counts are greater than 1 and no more than 20% of cells are less than 5
Fisher's Exact Test
- Used if Chi-Square assumptions are not met
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