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>> So the two key terms you
hear a lot in assessment.

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We often use it to evaluate assessments
are validity which we've just talked about

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and reliability which we've talked about
actually throughout issues of reliability.

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Reliability is the consistency of what
we're measuring and perhaps the consistency

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of the evidence in that way, okay.

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So we want to limit the impact of
factors that aren't language so that

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when we collect evidence, we're just
finding out what we can about language.

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We can never eliminate all of
the factors that impact it.

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So when we were talking about performance
assessment, things like anxiety, creativity,

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background knowledge, we can't get rid of those
things on students' performances, but we--

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what we try to do is limit
them as much as possible.

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And reliability in a very basic sense, if
you think about someone taking a test today

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and taking the same test tomorrow
assuming there is no practice effect

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and that their language hadn't
improve considerably overnight,

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their score should be pretty
much the same, okay.

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So in the well-designed test, that's
one thing we're trying to achieve.

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In terms of classroom assessment, we want
to think about first what we want to assess

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and then find the best ways
to gather that evidence

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so that we have some validity
in our assessment practices.

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At the same time, we're trying to collect
evidence in a consistent way, okay.

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And in a way that will limit, delimit
the factors that aren't language ability

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or what we want to assess and
that is the reliability, okay.

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Now reliability-- sometimes we talk about
internal reliability which is in the test.

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So, if you have a long test with lots
of items, there are various ways to look

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at the reliability of those items.

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But what we see in classroom assessment in
terms of reliability often has more to do

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with the rubrics that we use, the
kind of test tasks that we design,

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theconditions that the students have like how
much time to work on it and if they're working

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with other people, things
that students often see

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as fairness actually do tie in to reliability.