Chapter 21 COMPARING TWO PROPORTIONS
Chapter 21
COMPARING TWO
PROPORTIONS
Objectives
?
?
?
?
Sampling distribution of the
difference between two proportions
2-proportion z-interval
Pooling
2-proportion z-test
Comparing Two Proportions
?
?
Comparisons between two
percentages are much more common
than questions about isolated
percentages. And they are more
interesting.
We often want to know how two
groups differ, whether a treatment is
better than a placebo control, or
whether this year¡¯s results are better
than last year¡¯s.
Another Ruler
?
?
In order to examine the difference
between two proportions, we need
another ruler¡ªthe standard deviation
of the sampling distribution model for
the difference between two
proportions.
Recall that standard deviations don¡¯t
add, but variances do. In fact, the
variance of the sum or difference of
two independent random quantities is
the sum of their individual variances.
The Standard Deviation of the Difference
Between Two Proportions
?
?
Proportions observed in independent
random samples are independent. Thus,
we can add their variances. So¡
The standard deviation of the difference
between two sample proportions is
SD ? p?1 ? p? 2 ? ?
?
p1q1 p2 q2
?
n1
n2
Thus, the standard error is
SE ? p?1 ? p? 2 ? ?
p?1q?1 p? 2 q?2
?
n1
n2
................
................
In order to avoid copyright disputes, this page is only a partial summary.
To fulfill the demand for quickly locating and searching documents.
It is intelligent file search solution for home and business.
Related searches
- comparing two similar stories
- comparing two percentages calculator
- two proportions hypothesis test
- z test for two proportions calculator
- comparing two percentages
- comparing two population means calculator
- test statistic comparing two means calculator
- t test comparing two means
- two proportions z test
- comparing two stories
- comparing two numbers percentage
- difference between two proportions calculator