# Week 11 Study Notes

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13 Dec 2010
School
Department
Course
Professor
GGR 270 Lecture 11 November 24, 2010
P- Value
Decision to reject or fail to reject h0 is made by comparing the test statistic to a
critical value of z or t
But, different significance levels may lead to different conclusions
To avoid ambiguity, some researchers prefer to use a variable level of significance P
value
Smallest value of a for which the h0 can be rejected
Actual risk of committing type 1 error
2 samples
In comparing 2 samples, if the sample means are significantly different, can
conclude they were drawn from different populations
2 sample difference of means test
Must examine difference in sample means
oIf sample difference is large, likely conclusion is the population means are
different
Need to know variances
oWe end up using 2 approaches according to whether we believe the variances
are equal or now
Both scenarios use T Statistic
Formulas
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## Document Summary

Ggr 270 lecture 11 november 24, 2010. decision to reject or fail to reject h0 is made by comparing the test statistic to a critical value of z or t. but, different significance levels may lead to different conclusions. To avoid ambiguity, some researchers prefer to use a variable level of significance p value. smallest value of a for which the h0 can be rejected. actual risk of committing type 1 error. In comparing 2 samples, if the sample means are significantly different, can conclude they were drawn from different populations. must examine difference in sample means: if sample difference is large, likely conclusion is the population means are different. need to know variances: we end up using 2 approaches according to whether we believe the variances are equal or now. 2 sample means test requires that we make a decision on whether or not to pool sample variances.