(a) Lets says I have a dataset of students' scores for 2 subjects when
tested in the 4th grade, and their scores on similar tests taken in the 6th
grade. Some students are lost between the 4th and 6th grade but some show
up in both grades. The data structure is as follows ...
ID grade subject score
A1 04 English 271
A1 04 Mathematics 190
A1 06 English 260
A1 06 Mathematics 214
A2 04 English .
A2 04 Mathematics 165
A2 06 English 187
A2 06 Mathematics 193
A3 04 English .
A3 04 Mathematics .
A3 06 English 216
A3 06 Mathematics 265
How would I create a subset of these data such that the subset only
contains records for students with non-missing scores in a given subject on
BOTH the 4th and the 6th grade tests?
(b) In the same dataset, let us assume there are multiple records for some
students on a single grade and subject. For example,
A4 04 English 191
A4 04 English 219
Of these multiple records, how can I select entries with the HIGHER SCORE?
(i.e., the lower scores have to be discarded).
I'm sure there is a quickfire way to solve both so I'd be grateful if
someone points me in the right direction in STATAspeak (9.1).
By the way, the N is about 3 million, though the number of unique student
IDs is about 250,000.
