Abbreviated Interrupted Time-Series - Institute for Policy Research
Abbreviated Interrupted Time-Series - Institute for Policy Research
Abbreviated Interrupted Time-Series - Institute for Policy Research
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Analytic Model<br />
• NCLB Public vs. Catholic school contrast<br />
• Model<br />
Y<br />
tj<br />
= β + β ( year)<br />
0<br />
+ β ( policy×<br />
group)<br />
6<br />
1<br />
• Low Power<br />
• Only 3 groups (public, Catholic, non‐Catholic private) with 8 time<br />
points. So only 24 degrees of freedom<br />
• Autocorrelation<br />
– Few solutions<br />
tj<br />
+ β ( group)<br />
2<br />
tj<br />
+ β ( policy)<br />
+ β ( policy×<br />
year×<br />
group)<br />
7<br />
+ β ( year×<br />
group)<br />
+ ε ,<br />
– Cannot use clustering algorithm because there are not enough groups<br />
– Robust s.e. used but results less conservative<br />
j<br />
3<br />
tj<br />
4<br />
tj<br />
tj<br />
tj<br />
+ β ( policy×<br />
year)<br />
5<br />
tj
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