What is the connection between a scatter plot and a calculation ...

[darbym82]

What is the connection between a scatter plot and a calculation of correlation? (Select all that apply.)
 
  a. Constructing a scatter plot allows the researcher to visualize in advance whether a calculation of linear correlation is likely to reveal a relationship between the variables.
  b. Constructing a scatter plot produces a correlation coefficient, as does calculating correlation.
  c. A calculation of correlation should be performed before constructing a scatter plot, because the calculation is more scientific.
  d. The scatter plot provides a visual representation of the connection between two variables; a correlational calculation provides a quantification of the connection between the same variables.
  e. Just like calculation of correlation, constructing a scatter plot provides a way to quantify explained variance.

Question 2

In the results and conclusions sections of a research article about adult morbid obesity and a history of being underweight during the first two years of life, the researcher mentions the strong negative correlation between these two variables.
 
  What does the author imply by stating this? (Select all that apply.)
  a. Some sort of test of correlation was performed and it reached statistical significance.
  b. A person with morbid obesity is more likely than someone without it to have been underweight during the first two years of life.
  c. A person with morbid obesity is less likely than someone without it to have been underweight during the first two years of life.
  d. Having been underweight during the first two years of life prevents morbid obesity in adulthood.
  e. The researchers avoided a type I error, in relation to the association between these two variables.
  f. The researchers operationalized the two study variables.

[kingfahad97]

Answer to Question 1

ANS: A, D
Scatter plots or scatter diagrams provide useful preliminary information about the nature of the relationship between variables. The researcher should develop and examine scatter diagrams before performing correlational analysis. Scatter plots may be useful for selecting appropriate correlational procedures, but most correlational procedures are useful for examining linear relationships only. A scatter plot can easily identify nonlinear relationships; if the data are nonlinear, the researcher should select statistical alternatives such as nonlinear regression analysis. A scatter plot is created by plotting the values of two variables on an x and y axis.

Answer to Question 2

ANS: A, C, E
Correlational analysis provides two pieces of information about the data: the nature or direction of the linear relationship (positive or negative) between the two variables and the magnitude (or strength) of the linear relationship. In a negative linear relationship, when one value is high, the other value tends to be low. The probability of rejecting the null hypothesis when it is in fact true is called type I error, and it is impossible to know whether it has occurred until replication research takes place. Operationalization of a variable indicates how it will be measured or manipulated in a study; without operationalization, no measurement can occur.