Hi:
When doing analysis for problems with a small
sample, a popular way is to replace the z-test to t-test.
However, there is still another approach, the re-sampling
method. One can repeatedly and randomly draw "new"
samples from the original sample set to form another
sample set. After a set fo "new" sample sets are built,
one can do analysis on these sample sets. But what
does this type of approach helps to "cure" the
problem of having a small sample set? Does it help
improve the power of analysis or else?
On Tue, 7 Jan 2020 11:32:24 -0800 (PST), Cosine <asecant@gmail.com>
wrote:
Hi:
When doing analysis for problems with a small
sample, a popular way is to replace the z-test to t-test.
However, there is still another approach, the re-sampling
method. One can repeatedly and randomly draw "new"
samples from the original sample set to form another
sample set. After a set fo "new" sample sets are built,
one can do analysis on these sample sets. But what
does this type of approach helps to "cure" the
problem of having a small sample set? Does it help
improve the power of analysis or else?
What you are describing is called "bootstrap".
It is used for circumstances where the direct computation
of the variance is hard to define, or is made unreliable by
oddities of the distribution.
The t-test is simple. Thus, it is not improved by bootstrapping.
The choice between assuming "common variance" and
"separate variances" for the two groups should depend
on expectations based on expectations a professional in
the area would have for the data, not on the test (in SPSS,
say) that tells you that "variances are unequal."
The biggest help for robustness of t-testing is the
willingness to perform a transformation that produces
a scale that is "interval" in terms of whatever the
hypotheses are about. (For instance: chemical
concentrations in biological processes are typically
compared as "twice as much" or "ten times as much" -
implying that those processes merit taking the logs
of the raw concentrations, to produce "equal intervals."
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