# Questions tagged [z-test]

The z-test is a statistical test for hypothesis testing that uses the standard normal distribution as the sampling distribution of the test statistic. A common example is the test for the difference of two proportions.

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46 views

### Comparing z-values

If a test-statistics is expressed in z-values (instead of, for example, t-values), would it be appropriate to use those values for some further inferences? For example, to average a pair and another ...
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### Significance of the difference between means

I am running an experiment on students in two of my classes. There is an online class vendor that promises higher test scores with only 2-3 hours more work per week. I decided to give one of my ...
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### What hypothesis test should I use to compare the overall performance of two different athletes in a 100m race?

I am sourcing data from IAAF's website to test my hypothesis - Athlete A is a better athlete than Athlete B (comparing their times in the Olympics). Since I would be sourcing the data from IAAF's ...
48 views

### Can I use a Z test?

Can i use a Z test for 2 proportions for the following data? I have 2 samples - male (N=33) and female (N=51) Within the male sample no-one tested positive for a particular attribute. 33 Tested ...
790 views

### Which statistical test should I use (comparing two cohorts)?

So I am doing some research in the field of Medical Physics, in particular radiation treatment with photons and protons. Now, I have two cases I am unsure about. 1) Here I have several patients. ...
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### Multiple planned comparisons of frequencies (based on a binary DV and multiple IV's)

I'm looking for the most appropriate way to to conduct multiple planned comparisons of frequencies. I conducted an experiment in which participants could come from one of two groups, 'Group A' and '...
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### Comparing two vector of pecentages

Say, I have two vector of percentages (in this particular case, percentages represent a proportion of certain cell types in blood samples). Both vectors sum up to 1. For example, there are vectors ...
556 views

### Standard error of reconstructed slopes (coxph/coxme)

I have performed mixed effect Cox hazard regressions, and reconstructed the slopes to get group specific slopes (e.g. sex-specific responses to the explanatory variable). I aim to test whether the ...
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### Testing variables in meta-analysis

I am conducting a meta-analysis of cognitive-behavioural interventions on self-esteem and I could use some assistance navigating through the statistical procedures. I have extracted pre-post scores ...
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### Probability that two people get a certain number of heads on 100 coin tosses and all other outcomes with lower probability?

2 people flip a coin 100 times. The first person get 42 heads, the second person gets 58 heads. What is the probability of this outcome and all other possible outcomes that have an equal or lower ...
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### Test of single proportion - how do i know population proprotion?

I have a study where I did a sample size calculation using N=2800, CI=95%, margin or error = 3.5% to yield n=613. In the study (auditing of charts), I wanted to look at the error rate in my sample. I ...
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### Z-test with a lot of null values

I have a question concerning the validity of my email tests. I'm testing different email variations (between 2 and 4 variations usually) with different groups of members (hundreds of thousands ...
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### Comparing proportions of 3 groups using chi square and z-test

I was wondering if my plan for analyzing my data was appropriate: I am trying to compare proportions between samples from 3 populations (N= 53, 54, and 56). I ran a chi squared test and found a ...
118 views

### two sample z test in r

I am dealing with a dataset like this below ...
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### Calculation of critical values

Are the critical values for the two-sample t-test with unequal variances calculated the same as for the two-sample z-test?
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### I'm comparing multiple demographics across multiple samples, Chi-square test or 2 sample t-test

I would like to compare the demographics of people my company serves with the demographics contained in a subset of the American Community Survey 2017 data. The first set (n=35751) of data is a person-...