The z-test tag has no wiki summary.
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3answers
48 views
Testing whether two groups formed from a continuous variable differ on a binary outcome
18 people, who have been divided into 2 groups based on the semiquantitative expression of a protein (low vs high).
Group 1 (low protein levels) has 6 people, Group 2 (high protein levels) has 12 ...
4
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1answer
60 views
Replace t-test with modified z-test - anyone ever seen this?
I just read about a procedure I'd never heard of, and was wondering if anyone has had any experience with it. In Donald Berry's "Statistics" book, he presents an alternative to doing a t-test by ...
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1answer
54 views
Testing for differences, would I use ANOVA?
I have four age groups all measuring different heights: How would I test for difference between the groups at 0.01 level of significance? Would I use ANOVA?
Also - how could I establish which group ...
2
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1answer
169 views
is the z-test for difference of proportions valid for massive samples with tiny proportions?
Let's say I want to run a difference of proportions test where each side has n=23,000 but their proportions are 0.21% and 0.34%.
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1
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1answer
167 views
Comparing change in average in two groups: Z-test?
I'm about to start up a project (as a high school teacher) that involves comparing the change in average between two different groups.
It's an experiment, and the setup is the following:
Obtain a ...
4
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2answers
257 views
Likelihood-ratio test or z-test?
Consider the following two logistic regression models:
$$
\begin{aligned}
&\text{Model A: }&P(Y=1)&=\frac{\text{exp}\left(b_1+b_2X_2\right)}{1+\text{exp}\left(b_1+b_2X_2\right)} \\
...
1
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1answer
85 views
Appropriate test for comparing two sets of binary tests?
I have items made from two different materials. For each material I took a set of 250 samples and subjected them to a test which either broke them or did not.
Which test could answer the question - ...
0
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1answer
79 views
Confusion related to significance test
I am trying to read the significance tests. However, I am a bit confused what exactly is the difference between chisquared test and z test. I read that chisquared is non parametric and it doesn't make ...
1
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2answers
367 views
Outlier detection for heavy-tailed data
Applying modified z-score for outlier elimination on some data (Iglewicz and Hoaglin, 1993), I discovered that a big proportion of the data (~10%) was outside the range ...
1
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1answer
180 views
Two-sample test of proportions
In my research, I aim to compare websites and need to identify if the websites differ significantly from each other. I have divided the website into two categories. I have sampled 45 websites in the ...
2
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2answers
420 views
Can I compute a confidence level for a z-test based on the size of the samples?
I'm doing a two sample z-test for the difference between means using pooled variance.
Suppose I've run two experiments. In the first experiment, the sample size for the two populations is only 100, ...
4
votes
1answer
125 views
Is the power for a Kappa test the same as underlying z-test?
The Kappa ($\kappa$) test is a Z-test kind of test. If I am not very wrong, to compute the $\kappa$ test, we can just estimate the appropriate variance $\hat {var}(\hat\kappa)$ for the kappa statistic ...
5
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1answer
200 views
Why is the power for this test so low?
What follows is a theoretical power calculation for a practice exam, but this seems very low. Did I do something wrong? The problem and solution is as follows:
In a drinks factory the mean fill of ...
