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S11.3 - Inference about Two Population Proportions
Inference about Two Population Proportions
27
Mathematics
Graduate
11/10/2013

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Term
4 assumptions of sampling distribution of the difference between two proportions
Definition
1. Sampling distribution of p1hat-p2hat is normal
2. And mean mew(p1hat-p2hat)=p1-p2
3. n1p1hat(1-p1hat)>=10
4. n2p2hat(1-p2hat)>=10
Term
p1hat =
Definition
x1/n1
Term
p2hat =
Definition
x2/n2
Term
mew(p1hat-p2hat) =
Definition
p1 - p2
Term
sigma(p1hat-p2hat) =
Definition
[(p1(1-p1)/n1)+(p2(1-p2)/n2)]^0.5
Term
Test statistic, z0 =
Definition
[(p1hat-p2hat)-(p1-p2)]/[(p1(1-p1)/n1)+(p2(1-p2)/n2)]^0.5
Term
Pooled estimate of p
Definition
The best point estimate of p because p is unknown
Term
When assuming null is true, p1-p2 = 0 so the new z0 =
Definition
(p1hat-p2hat)/[p(1-p)]^0.5 x [(1/n1)+(1/n2)]^0.5
Term
Pooled estimate of p, phat =
Definition
x1+x2/n1+n2
Term
When we substitute pooled estimate of p into z0 equation, we get test statistic two independent population proportions, z0 =
Definition
(p1hat-p2hat)/[phat(1-phat)]^0.5 x [(1/n1)+(1/n2)]^0.5
Term
3 assumptions for hypothesis test regarding the difference between two population proportions
Definition
1. The samples are indecently obtained using simple random sampling
2. n1p1hat(1-p1hat) > 10 and n2p2hat(1-p2hat) > 10
3. The sample size is no more than 5% of the population size
Term
Two-tailed test, two population proportions
H0:
H1:
Definition
H0: p1 = p2
H1: p1 not=to p2
Term
Left-tailed test, two population proportions
H0:
H1:
Definition
H0: p1 = p2
H1: p1 < p2
Term
Right-tailed test, two population proportions
H0:
H1:
Definition
H0: p1 = p2
H1: p1 > p2
Term
Two-tailed test, classical approach
If z0 > z(alpha/2), then
Definition
Reject the null
Term
Left-tailed test, classical approach
If z0 < -zalpha, then
Definition
Reject the null
Term
Right-tailed test, classical approach
If z0 > zalpha, then
Definition
Reject the null
Term
If p-value < alpha then
Definition
Reject the null
Term
If p-value > alpha then
Definition
Fail to reject null
Term
3 assumptions for constructing a confidence interval for difference between two population proportions
Definition
1. The samples are indecently obtained using simple random sampling
2. n1p1hat(1-p1hat) > 10 and n2p2hat(1-p2hat) > 10
3. The sample size is no more than 5% of the population size
Term
Lower bound CI, two population proportions =
Definition
(p1hat-p2hat) - z(alpha/2) x [(p1hat(1-p1hat)/n1)+(p2hat(1-p2hat)/n2)]^0.5
Term
Upper bound CI, two population proportions =
Definition
(p1hat-p2hat) + z(alpha/2) x [(p1hat(1-p1hat)/n1)+(p2hat(1-p2hat)/n2)]^0.5
Term
2 assumptions for testing a hypothesis regarding the difference of two proportions with dependent samples (McNemar's Test)
Definition
1. The samples are dependent and are obtained randomly
2. The total number of observations where the outcomes differ must be greater than or equal to 10 (f12+f21>=10)
Term
Test statistic, two matched pairs proportions z0 =
Definition
[abs val(f12-f21) - 1]/(f12+f21)^0.5
Term
Margin of error for population proportions, E =
Definition
z(alpha/2) x [(p1hat(1-p1hat)/n)+(p2hat(1-p2hat)/n2)]^0.5
Term
Sample size for estimating p1-p2, n = n1 = n2 =
Definition
[p1hat(1-p1hat) + p2hat(1-p2hat)](z(alpha/2)/E)^2
Term
Sample size for estimating p1-p2 is p1 and p2 are unavailable, n = n1 = n2 =
Definition
0.5[z(alpha/2)/E]^2
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