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Educational Research: Causal-Comparative Studies

Educational Research: Causal-Comparative Studies. EDU 8603 Educational Research Richard M. Jacobs, OSA, Ph.D. Research. The systematic application of a family of methods employed to provide trustworthy information about problems.

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Educational Research: Causal-Comparative Studies

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  1. Educational Research: Causal-Comparative Studies EDU 8603 Educational Research Richard M. Jacobs, OSA, Ph.D.

  2. Research... • The systematic application of a family of methods employed to provide trustworthy information about problems …an ongoing process based on many accumulated understandings and explanations that, when taken together lead to generalizations about problems and the development of theories

  3. The basic steps of research... Scientific and disciplined inquiry is an orderly process, involving: recognition and identification of a topic to be studied (“problem”) description and execution of procedures to collection information (“method”) objective data analysis statement of findings (“results”)

  4. Research methods... Quantitative… …collects and analyzes numerical data obtained from formal instruments

  5. Quantitative methods... • descriptive research (“survey research”) • correlational research • causal-comparative research (“ex post facto research”) • experimental research

  6. causal-comparative research (“ex post facto research”) …at least two different groups are compared on a dependent variable or measure of performance (called the “effect”) because the independent variable (called the “cause”) has already occurred or cannot be manipulated

  7. Research variables... Independent… …an activity of characteristic believed to make a difference with respect to some behavior …(syn.) experimental variable, cause, treatment

  8. dependent variable… …the change or difference occurring as a result of the independent variable …(syn.) criterion variable, effect, outcome, posttest

  9. A causal-comparative study… …a study in which the researcher attempts to determine the cause, or reason, for pre-existing differences in groups of individuals …called an “ex post facto” study because both the effect and the alleged cause have already occurred and must be studied in retrospect

  10. Differences in causal-comparison and correlational studies… • causal-comparative studies… …attempt to identify cause-effect relationships • correlational studies… …attempt to identify relationships

  11. causal-comparative studies… …involve two (or more) groups and one independent variable • correlational studies… …typically involve two (or more) variables and one group

  12. causal-comparative studies… …involve making comparisons • correlational studies… …involve establishing relationships

  13. Differences in causal-comparison and experimental studies… • causal-comparative studies… …individuals are not randomly selected but selected because they belong to groups • experimental studies… …individuals are randomly selected and assigned to two (or more) groups

  14. causal-comparative studies… …the researcher cannot manipulate the independent variable • experimental studies… …the researcher manipulates the independent variable

  15. causal-comparative studies… …the independent variable has already occurred and cannot be manipulated • experimental studies… …the researcher manipulates the independent variable to determine its effects

  16. causal-comparative studies… …the random sample is selected from two already-existing populations • experimental studies… …the random sample is selected from a single population

  17. Conducting a causal-comparative study… 1. select the problem 2. select participants and instrument 3. design and procedure 4. data analysis and interpretation

  18. 1. select the problem… …the researcher starts with an effect and seeks its causes …the independent variable cannot or should not be manipulated

  19. 2. select the participants and instrument… …select samples representative of their respective populations and similar with respect to critical variables other than the independent variable …called “comparison groups”

  20. 3. design and procedure… …the performance of the groups is compared using some valid dependent variable measure (“instrument”) …lack of randomization, manipulation, and control are sources of weakness

  21. control …the process by which the researcher attempts to ensure that the findings are as free of researcher bias and error as possible

  22. types of control …random assignment of participants to groups …pair-wise matching …comparing homogeneous groups …comparing homogeneous subgroups …factorial analysis of variance …analysis of covariance

  23. random assignment of participants to groups …not possible in causal-comparative studies because the groups already exist and have already received the treatment

  24. pair-wise matching …first: find a participant in the second (third, fourth, etc.) group with the same or similar score on the control (nonmanipulated) variable as the participant in the first group …second: if a participant in either group does not have a suitable match, the participant is eliminated from the study

  25. comparing homogeneous groups …control for extraneous variables that are homogeneous with respect to the extraneous variables …limitation: lowers the number of participants in the study and, of course, limits the generalizability of the findings

  26. comparing homogeneous subgroups …form subgroups within each group that represent all levels of the control (nonmanipulated) variable …controls for the variable and also permits the researcher to determine whether the independent variable affects the dependent variable differently at different levels of the control (nonmanipulated) variable

  27. factorial analysis of variance (“FANOVA”) …building the control (nonmanipulated) variable into the research design …then use FANOVA to analyze the results to determine the effect of the independent and control (nonmanipulated) variable on the dependent variable, both separately and in combination

  28. …FANOVA allows the researcher to determine if there is an interaction between the independent variable and the dependent variable such that the independent variable operates differently at different levels of the independent variable building it into the research design

  29. analysis of covariance (“ANCOVA”) …statistically adjusts initial group differences on a dependent variable for initial differences on some other variable related to performance on the dependent variable …removes initial differences so that the results can be fairly compared as if the two groups started equally

  30. symbolic representation of the basic causal-comparative design Independent Dependent GroupVariableVariable (E) (X) O (C) O Where: E (experimental group); C (control group); X (independent variable); O (dependent variable)

  31. Independent Dependent GroupVariableVariable (E) (X1) O (C) (X2) O Where: E (experimental group); C (control group); X (independent variable); O (dependent variable)

  32. 4. Data analysis and interpretation… …researcher uses a variety of descriptive and inferential statistics: t-test mean analysis of variance standarddeviation chi squared

  33. mean …the descriptive statistic indicating the average performance of an individual or group on a measure of some variable

  34. standard deviation …the descriptive statistic indicating the spread of a set of scores around the mean

  35. t-test …the inferential statistic indicating whether the means of two groups are significantly different from one another

  36. analysis of variance (“ANOVA”) …the inferential statistic indicating the presence of a significant difference among the means of three or more groups

  37. chi squared (Χ2) …the inferential statistic indicating that there is a greater than expected difference among group frequencies

  38. Mini-Quiz… • True and false… …causal-comparative studies attempt to identify the cause-effect relationships; correlational studies do not True

  39. …causal-comparative studies typically involve two (or more) groups and one independent variable, whereas correlational studies typically involve two (or more) variables and one group True

  40. …causal-comparative studies involve relation, whereas correlational studies involve cause False

  41. …oftentimes, causal-comparative research is undertaken because the independent variable could be manipulated but should not True

  42. …one of the most important reasons for conducting causal-comparative research is to identify variables worthy of experimental investigation True

  43. …“lack of control” means that the researcher can and should manipulate the independent variable False

  44. …each group in a causal-comparative study represents a different population True

  45. …the more similar two groups are on all relevant variables except the independent variable, the stronger the study is True

  46. …there is random assignment to treatment groups from a single population in causal-comparative studies False

  47. …lack of randomization, manipulation of the independent variable, and control are all sources of weakness in a causal-comparative design True

  48. …matching, comparing homogenous groups or subgroups, and covariate analysis are strategies that enable researchers to overcome problems of initial group differences on an extraneous variable True

  49. …interpretation of the findings in a causal-comparative study requires considerable caution because the cause may be the effect and the effect may be the cause True

  50. …extraneous variables or confounding factors may be the real “cause” of both the independent and dependent variables True

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