8/18/2019 After All the Pairs Have Been Formed
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After all the pairs have been formed,’ we randomly assign
one
member of each pair to a treatment condition. We can do this
simply bý
flipping a coin.It is very important to put the members of each
pair into
the treatment conditions at random. If we do not, we could
create a new
source of confoundIng exactly what we are trying to avoid.
in our cockroach example, the matching is done before the
experiment is run. In some experiments it might not be feasible
to do the
matching beforehand. uppose we need to match our sub!ects on
intelligence.
We might not be able to give an intelligence test, score it,
match and
assign sub!ects to groups, and run the actual experiment in a
single block
of time. We must know the test scores before we can do the
matching, so we
might need
a separate testing session !ust to give’ the test. In these
situations we could proceed differently. We make the initial
assignment to
conditions at random and run the experiment with two randomly
assigned
groups of sub!ects that might or might not be comparable on our
matchingvariable. "ur sub!ects take part in the treatment
conditions as usual.
#owever, we also give them the intelligence test $that is, we
measure them
on the matching variable%. When the.experiment is. over, we use
the
intelligence test scores to match. the sub!ects across the two
groups,
discarding those sub!ects in each group who cannot be
matched.
We can do this in thrce ways We may use precision matching in
which
we insist that the members of the matched pairs have identical
scores. A
more common procedure is range matching in which we re&uire
that the
members of a pair fail within a previously specined range of
scores. 'he
process of range matching sub!ects after the experiment is run
is
illustrated in 'able ()*. In the table you can see that sub!ects
are
considered matched if their scores fall within + points of each
other. 'hechoice of range is arbitrary 'he smaller the range,
however, the more
Setelah semua pasangan telah dibentuk,' kami secara acak
menetapkan satuanggota dari setiap pasangan untuk pengobatan
kondisi. Kita dapat melakukanini hanya bý membalik koin. Hal ini
sangat penting untuk menempatkan anggotasetiap pasangan ke kondisi
perawatan secara acak. Jika kita tidak, kita bisamenciptakan sumber
baru membingungkan persis apa kita berusaha untukmenghindari.
dalam contoh kita kecoa, pencocokan dilakukan sebelum percobaan
dijalankan.Di beberapa eksperimen tidak mungkin layak untuk
melakukan pencocokansebelumnya. isalkan kita perlu untuk
mencocokkan subyek kami padakecerdasan. Kita tidak mungkin mampu
memberikan tes kecerdasan, Skor ini,cocok dan menetapkan mata
pelajaran untuk kelompok, dan menjalankanpercobaan yang sebenarnya
dalam satu blok waktu. Kita harus tahu nilai tessebelum kita bisa
melakukan yang cocok, jadi kita mungkin perlu
sesi pengujian terpisah hanya untuk memberikan ' tes. Dalam
situasi ini kitadapat melanjutkan berbeda. Kami membuat tugas awal
untuk kondisi secaraacak dan menjalankan percobaan dengan dua
ditugaskan secara acak kelompokmata pelajaran yang mungkin atau
mungkin tidak sebanding pada !ariabelcocok kami. Subyek kami
mengambil bagian dalam pengobatan kondisi sepertibiasa. "amun, kami
juga memberikan mereka tes kecerdasan #maksudnya, kita
