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. Author manuscript; available in PMC: 2010 Sep 1.
Published in final edited form as: Psychol Aging. 2009 Sep;24(3):563–573. doi: 10.1037/a0015511

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Two-slope Latent Growth Curve Model. Observed data are denoted by IPT1 through IPT6. Mi = mean intercept; Ms1 = mean slope 1; Ms2 = mean slope 2; U1 through U5 indicate random error. I*, S1*, and S2* refer to the standardized scores of I, S1, and S2. Di denotes deviations from the group intercept and Ds1 and Ds2 denote deviations from the group slopes. The correlations among the growth curve parameters are indicated by Ris1, Ris2, and Rs1s2. The paths from the latent slopes to the observed scores are the age basis coefficients, B1t and B2t, which define the intervals of change over age.