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STATS 240- Chapter 2
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- 1What does it mean when two variable are associated?Signifies a relationship between two variables. The value of one variable tells you something about the value of the other variable
- 2What is a response variable?A response variable measures or records an outcome of a study
- 3What is an explanatory variable?Explanatory variables explain changes in the response variable
- 4What axis are response variables plotted?Y-axis
- 5What axis are explanatory variables plotted on?x-axis
- 6What are 5 key characteristics of data for relationships?1. Cases
2. Categorical/quantitative
3. Values
4. Explanatory/Response
5. Label - 7What three ways can we describe a relationship on a scatterplot?1. Form
2. Direction
3. Strength - 8What do scatterplots display?2 quantitative variables
- 9How would you describe the form of a scatterplot?Linear or non-linear
- 10How would you describe the direction of a scatterplot?Positive or negative
- 11What is positive association?High values of one variable tend to occur together with high values of the other variable
- 12What is a negative association?High values of one variable tend to occur together with low values of the other variable
- 13How does one describe strength of a scatterplot?Strength of the relationship between the two variables can be seen by how much variation, or scatter, there is around the mean
- 14What are considered outliers on a scatterplot?Outliers are points that fall outside of the overall pattern of the relationship
- 15How are categorical data displayed on a scatterplot?The different data is displayed by using different colors on a scatterplot
- 16What happens when the explanatory variable is categorical?You cannot use a scatterplot. You can use back-to-back stemplots or side-to-side boxplots
- 17What does the correlation (r) tell us?The measure of direction and strength of the linear relationships between two quantifiable variables
- 18Can r be used to describe categorical variables?r can only be used to describe quantifiable variables
- 19When would the value of r be positive?When there is a positive association between the variables
- 20When would the value of r be negative?When there is a negative association between the variables
- 21Can r tell the difference between response and explanatory variables?No is cannot
- 22What values can r have?r can be between -1 and 1
where:
-1 indicates a strong negative relationship
1 indicates a strong positive relationship
0 indicates a weak relationship - 23Is r resistant?No, r is not resistant. The value of r is strongly impacted by outliers
- 24Does r have any units?Np, r does not have any units.
- 25Can r be used to describe non-linear relationships?No, r cannot be used to describe non-linear relationships, ONLY linear
- 26What is a regression line?A regression line summarizes the relationship between two variables but only when one variable explains/predicts the other
- 27Why do we use a regression line?We use a regression line to make a prediction of the response variable for a value of the explanatory variable
- 28How do we draw a regression line?Fitting a line is the best way to draw a regression line. A best-fit line that comes as close as possible to all of the points
- 29When drawing a regression line, what is the goal?To minimize the distance between the actual value and the predicted value
- 30True or False: There is a close correlation between correlation and the slope of the least squares regression line?True
- 31True or False: The least squares regression line always passes through the mean?True
- 32True or False: The distinction between explanatory and response variable is essentialTrue- if these variables get mixed up then you will get the wrong line
- 33What is the difference between correlation and regression?Correlation: Measure of spread (scatter) in both the x and y directions in a linear relationship
Regression: Examine the variation in the response variable (y) given change in the explanatory variable (x) - 34Can you use a calculated least squares regression line for any range?No, the least squares regression line is specific to predict y for any x within the range studied
- 35What is the coefficient of determination (r2)It is the square of r
r squared represents the percentage of the variance in y that can be explained by changes in x - 36Why are two-way tables used?Two-way tables show relationships between two categorical variables, both measured on the same individual
- 37What are joint distributions?Joint distributions are a collection of proportions. Simply find the proportion for each row and cell within a two-way table
- 38What are marginal distributions?Marginal distributions are distributions for a single categorical variable
- 39What is the Simpson's paradox?An association or comparison that holds for all of several groups can reverse direction when the data are combined to form a single group or "reversal of comparison by aggregation"
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- TOEFL STATS 240 Fichas sobre STATS 240- Chapter 2, creado por Mariah Kampman el 04/02/2022.
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- Mariah Kampman
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