Hi everyone,
I am running a multilevel linear regression with one continuous Level 1 independent varialbe (x). As can be seen in the syntax below, a random intercept is specified. I have a question regarding the interpretation of this random effect, because the value generated in the output (Intercept [subject = ID] Variance is substantially greater than the intercept value from the fixed effect. I understand that the intercept value from the fixed effect represents the average outcome value when X=0 and that the random effect is different, but the difference in these values is extremely large (i.e., fixed intercept value = *4.4*; Intercept variance = *385.6*). Perhaps this huge intercept variance simply reflects the huge between-person differences in mean outcome values, but I'm still wondering if this type of difference can happen. Here's the syntax below: MIXED y WITH x /PRINT=SOLUTION TESTCOV /METHOD=ML /FIXED= x /RANDOM INTERCEPT | SUBJECT(ID) COVTYPE (ID) /REPEATED=Wave | SUBJECT(ID) COVTYPE(AR1) . Thanks in advance for your assistance. O. -- Sent from: http://spssx-discussion.1045642.n5.nabble.com/ ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
Oliver,
I'm curious. Why do you have a repeated specification as well as a random specification? What is the structure of your data? Gene Maguin -----Original Message----- From: SPSSX(r) Discussion <[hidden email]> On Behalf Of Oliver Sent: Thursday, October 29, 2020 10:02 AM To: [hidden email] Subject: Intercept variance (Mixed modeling) Hi everyone, I am running a multilevel linear regression with one continuous Level 1 independent varialbe (x). As can be seen in the syntax below, a random intercept is specified. I have a question regarding the interpretation of this random effect, because the value generated in the output (Intercept [subject = ID] Variance is substantially greater than the intercept value from the fixed effect. I understand that the intercept value from the fixed effect represents the average outcome value when X=0 and that the random effect is different, but the difference in these values is extremely large (i.e., fixed intercept value = *4.4*; Intercept variance = *385.6*). Perhaps this huge intercept variance simply reflects the huge between-person differences in mean outcome values, but I'm still wondering if this type of difference can happen. Here's the syntax below: MIXED y WITH x /PRINT=SOLUTION TESTCOV /METHOD=ML /FIXED= x /RANDOM INTERCEPT | SUBJECT(ID) COVTYPE (ID) /REPEATED=Wave | SUBJECT(ID) COVTYPE(AR1) . Thanks in advance for your assistance. O. -- Sent from: http://spssx-discussion.1045642.n5.nabble.com/ ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
Hi Gene,
Thanks for getting back to me. I have probably not provided enough details about the study design, but the outcome is assessed repeatedly (i.e., 14 times) for each ID (i.e., within-person). Same for the Level 1 independent variable. The repeated subcommand was thus used to specify the repeated measures. Thanks again for your assistance. O. -- Sent from: http://spssx-discussion.1045642.n5.nabble.com/ ===================== To manage your subscription to SPSSX-L, send a message to [hidden email] (not to SPSSX-L), with no body text except the command. To leave the list, send the command SIGNOFF SPSSX-L For a list of commands to manage subscriptions, send the command INFO REFCARD |
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