This is a cross-sectional descriptive study to investigate the actor and partner effects of parenting stress and co-parenting on marital conflicts and the differences between groups according to the mothers’ employment status utilizing the 8th Panel Study on Korean Children [Figure 1].
The present study included parents above the age of 19 years and their children who participated in the 8th Panel Study on Korean Children (2015). The Panel Study on Korean Children is a review of the newborns born in 2008 and their mothers and community environment, for which the data up to 8th survey have been released to the public. The Panel Study on Korean Children conducted by Korea Institute of Child Care and Education included all households of newborns born between April and July 2008, excluding those who were excluded from the survey and who refused to participate, from surveyed medical institutes with more than 500 or more annual births per year. The exclusion criteria of the newborn household were mothers who cannot communicate in Korean, mothers with poor health after giving birth, newborns with serious diseases, mothers with serious diseases, newborns awaiting adoption, multiple births, and mothers younger than 18 years old. The Panel Study on Korean Children recruited a pilot sample of 2,563 households, from which 2,150 newborn households were selected as the final sample. For the sampling of the Panel Study on Korean Children, a stratified multistage sampling method was applied; the first stage included selecting medical institutes where childbirth occurs, the second stage included extracting newborn households with newborns born in selected medical institutes as a pilot sample, and the third stage included establishing a sample from the pilot sample with households who wish to participate in the panel. The sample retention rate proposed by the Panel Study on Korean Children’s research team for the validity of this study sample was determined to be 74.3% for the 8th-panel survey. In this study, among all children who participated in the panel study and health questionnaire survey, 161 fathers and 161 mothers raising seven-year-old children recently treated for AD for 12 months were selected as the final study participants. In the structural equation model, the minimum recommendation for the sample size is 10 times the free parameter, and the ideal size is 150–400 participants, so 161 participants in this study constituted a sufficient sample size to analyze actor and partner effects using the structural equation model.
In the study, the validity of the tool was confirmed through confirmatory factor analysis. Convergent validity was confirmed to be greater than .50 for each factor loading, greater than .70 for construct reliability, and greater than .50 for average variance extracted, and discriminant validity was found to be valid when the AVE (averaged variance extracted) values of the different latent variables were greater than the square of the correlation coefficient between the latent variables.
For the parenting stress survey, “burden and distress from carrying out parents’ role” among the subfactors of the parenting stress scale developed by Kim and Kang  was extracted by the Panel Study on Korean Children’s research team, and a tool with 11 questions confirmed through a preliminary survey from 2007 was used. A total of 11 questions were based on a five-point scale, and higher scores signify high parenting stress. For the reliability of the tool in the study by Kim and Kang , Cronbach’s alpha was .86. For the reliability of the tool in this study, Cronbach’s alpha was .88 for the father and .90 for the mother. As a result of the confirmatory factor analysis, goodness of fit of the father’s parenting stress model was Chi square (χ²) = 26.24, degrees of freedom (df) = 24, Goodness of Fit Index (GFI) = .93, Adjusted GFI (AGFI) = .90, Normed Fit Index (NFI) = .92, Comparative Fit Index (CFI) = .94, Standardized Root Mean Square Residual (SRMR) = .03, Root Mean Squared Error of Approximation (RMSEA) = .02 with Critical Ratio (CR) = .92, AVE = .61. The goodness of fit of the mother’s parenting stress model was χ² = 70.49, df = 24, GFI = .93, AGFI = .90, NFI = .92, CFI = .94, SRMR = .04, RMSEA = .05 with CR = .91, AVE = .60.
For the co-parenting survey, the measurement tool developed by Mchale  was translated by the Panel Study on Korean Children’s research team, and a total of 16 questions (four subcategories: family unity, discipline, criticism, conflict), which underwent the preliminary survey, were selected based on a seven-point scale. Higher sum of scores signifies a high level of co-parenting. In Mchale’s study , the reliability of the tool was Cronbach’s alpha .59–.82, and, in this study, Cronbach’s alpha was .88 for the father and .86 for the mother. As a result of the confirmatory factor analysis, goodness of fit of the father’s co-parenting model was χ² = 34.23, df = 21, GFI = 95, AGFI = .91, NFI = .94, CFI = .96, SRMR = .04, RMSEA = .05 with CR = .83, AVE = .61. The goodness of fit of the mother’s co-parenting model was χ² = 31.13, df = 21, GFI = .97, AGFI = .92, NFI = .97, CFI = .98, SRMR = .05, RMSEA = .06 with CR = .86, AVE = .60.
For marital conflict, the measurement tool developed by Markman et al.  was translated and revised by the Panel Study on Korean Children’s research team, composed of a total of eight questions based on a five-point scale. The reliability of the tool in this study is as follows. Cronbach’s alpha for the father was .91, and that of the mother was .93. As a result of the confirmatory factor analysis, goodness of fit of the father’s marital conflict model was χ² = 49.55, df = 20, GFI = .93, AGFI = .90, NFI = .94, CFI = .96, SRMR = .02, RMSEA = .03 with CR = .94, AVE = .67. The goodness of fit of the mother’s marital conflict model was χ² = 56.32, df = 20, GFI = .92, AGFI = .90, NFI = .95, CFI = .97, SRMR = .03, RMSEA = .04 with CR = .94, AVE = .66.
The 8th Panel Study on Korean Children was approved by the institutional review board of the Korea Institute of Child Care and Education (IRB No. KICCEIRB-2015-03). The current work was also conducted after review by the Institutional Review Board of C University.
Data collection and analysis
The data were obtained from the website of the Panel Study on Korean Children (http://panel.kicce.re.kr/kor/publication/02.jsp). For the use of Panel Study on Korean Children’s data, the study protocol was submitted to the Panel Study on Korean Children’s research team and reviewed. After obtaining the approval to use the 8th Panel Study on Korean Children’s data, the corresponding data were downloaded. The collected data were analyzed using SPSS-WIN Version 20.0 and AMOS Version 20.0 programs. The descriptive statistics of SPSS were used for the participants’ general characteristics and descriptive statistics of the measurement variables, the skewness and kurtosis of the measurement variables were verified for the normality of the data, and AMOS was used to confirm multivariate normality. In addition, the correlations and multicollinearity of each construct and the measurement variables were confirmed by Pearson’s correlation coefficient, and the reliability of the tool was confirmed by Cronbach's alpha coefficient. To confirm the actor and partner effects of parenting stress and co-parenting on marital conflict, the AMOS structural equation model was used. Furthermore, measurement invariance was conducted to confirm the homogeneity of the father and mother’s data within one measurement tool. To verify the goodness of fit of this study’s model, maximum likelihood method was used, and confirmatory factor analysis was used to confirm the validity of latent variables for model analysis. For the goodness of fit of the model, the absolute fit indices of χ2, χ2/df, RMSEA, SRMR, GFI, AGFI, CFI, NFI and Tucker-Lewis Index (TLI) were used. Direct effect, indirect effect, and statistical significance of total effect were confirmed using bootstrapping. To test the structural model invariance across the groups, an analysis technique that examines the difference in path coefficients between measurement models was used to compare the critical ratios of the free and constrained models.