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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a method to perform statistical test to test the diff of mean is larger than a threshold
I'm trying to test the difference of means of two groups, A and B, is larger than a specific value or not.
The two groups are considered as sampled from two binomial distributions and can be ...
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Find if two groups are different where one is a subset of the other
I have a dataset of 3,500,000 categorical observations that can be grouped by an ID. In these categories u occurs 25,000 times. How can I test to determine if a ...
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Hypothesis Testing for Means & Proportions. t-test vs z-test
How can I convince my teacher that he is wrong in this task? We were given the following task and my teacher says I have to use a z-test. In my opinion I have to use a t-test.The task is as follows:
A ...
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Can evidence of absence be obtained only in one-sided hypothesis tests?
It seems that if a one-sided Z-test returns a p-value $>1 - \alpha$, you have enough evidence of absence to reject the alternative hypothesis in favor of the null hypothesis, because if you were to ...
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OLS uses t-test but GLM uses z-test in statsmodels python
statsmodels library in python offers two different approaches for regression, ols and glm. While they are different methods, if the error is normally distributed, they should provide the exact same ...
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When testing significance between a regression coefficient of two data sets using a Z-test, how to interpret the z-value?
I am following the methods described in:
Clogg, C. C., Petkova, E., & Haritou, A. (1995). Statistical methods for comparing regression coefficients between models. American Journal of Sociology, ...
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How to perform a z-test for a 2d-gaussian?
I have N 2-dimensional points (X,Y) where X and Y are gaussian distributed and have a strong correlation, i.e., X and Y are not independent. What is the simplest way to perform a z-test? In other ...
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Statitical comparison of regression prediction to sample of data
I have a dataset, let's call it data1(x,y), where the data y is measured at 16 values of x. I use this dataset to fit to a 3-parameter model. I can obtain estimates for the three model coefficents ...
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Best stats test for a resume audit study evaluating bias
I am testing an applicant tracking system and giving it resumes that have implicit mention of race, and asking the system to rank them.
There is a control resume with no implicit mention of race.
For ...
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Z-test with no relevant sample size as I have a Gaussian probability distribution
I have two Gaussian curves, there are not samples, these are just probability distributions essentially. So I can do a Gaussian fit on them, or also a weighted average and weighted variance on the ...
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What is the best statistical measurement for collocational analysis?
I am a beginner with statistics and corpus linguistics, so sorry in advance if my explanation have gaps in it.
So I want to perform corpus linguistics collocational strength analysis on a given corpus,...
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Why use a z test rather than a t test with proportional data?
When testing the difference between 2 proportions why do we use a z-test rather than a t-test?
Further, is there a simple way to conduct an omnibus test for significant differences between more ...
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What would be appropriate test to compare two lists of dichotomous variables?
Colleagues, can't wrap my mind on simple question, please help!
I have two products and list of their attributes. My respondents make an answer which product on each attribute they prefer. Finally ...
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What A/B test calculator can I use to calculate the minimum same size for uneven split between control and treatment groups?
I have only come across A/B test calculators that give the minimum sample size per variation for 50-50 split between control and treatment.
I am running an A/B test for conversion rates with a 80/20 ...
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For a continuous distribution, can I replace the mean by the median in two sample z-test?
For a continuous distribution, can I replace the mean by the median in two sample z-test? Assuming that populations are normally distributed. I feel like they can because both median and sample mean ...
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Is a log transformation valid for a pre-experiment sample size calculation using 2-sided z test?
Goal
I am conducting a pre-experiment analysis to determine what the necessary sample size is given a specific power, significance level, and lift.
Data
This is for a research question where I have a ...
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Why do Z-tests use standard error (using the know population standard deviation) and not only standard deviation?
I understand why a T-test uses the standard error, after all we are dealing with the inaccuracy of small samples.
$$T = \frac{\bar{x} - \mu}{\bar{s} / \sqrt{n}} = \frac{\bar{x} - \mu}{SE} $$
But why ...
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Should I use a $\chi$-squared test or a z-test?
I have a dataset with four groups $G_i$ with $i = 1, 2 , 3 , 4$, and in each group $G_i$, a certain number $n_i$ of observations are favorable. I want to check if there are any differences between the ...
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Z Test basic problem
The mean selling price of new homes in a town over a year was \$2,200,000. The population standard deviation is \$200,000 . A random sample of 81 new home sales from this city was taken. What is the ...
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What distribution does $\frac{\hat p -p_0}{\sqrt{p_{0}(1-p_{0})/n}}$ have?
Suppose we're testing whether more than $100p_0$% Bernoulli trials are successful at the $\alpha$% significance level. We take a sample of $n$ Bernoulli trials and find that $\hat p$ trials are ...
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Z test for proportion of sums
I want to perform a Z-test for two variables: $ X $ (Buyer proportion) and $ Y $ (Spent proportion \$ ). Below the table you can see a dummy example of the data I have:
Let's assume the conditions ...
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Hypothesis testing on a model's inference
I have the following situation, which I've mapped to an example below.
At the conclusion of an A/B test done on a website I've a metric I care about. Let's assume its the number of users clicking on a ...
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Why is the sample standard deviation used in the z-test?
The assumption of the z-test is that the population standard deviation $\sigma$ is known. With this in mind I tried to manually compute the p-value for a (one-tailed) z-test that the sample mean $\bar{...
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One proportion Z-test and Chi Square Goodness of Fit should be identical but return different results
My understanding is that a Chi Square Goodness of Fit test and a one-proportion Z-test should have identical p-values and be equivalent (https://youtu.be/-Vssir6yUNQ?si=4-t9Np9h4bedU9xN&t=423). ...
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Z-test for One Population Proportion
I am completing a series of questions for this problem and I think I am following but one throws me off.
The problem is a common one:
In a study of smokers who tried to quit smoking with nicotine ...
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On the success or failure of an experiment
Recently I've been asked this question and I wasn't really able to give a solid answer from a statistical standpoint. I hope someone can help me :)
Statement
Let's say that in a given region, in a ...
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2 proportion Z/T test?
I want to find out if 2 proportions are different or not.
For one, sample size is <30.
For the other, it's much >30.
Can I use the Z test since one size is large? Or do i have to use the t test? ...
Tim♦
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Did I use z-test correctly in this problem?
The problem:
It has been said that it is difficult to distinguish Coke and Pepsi by taste alone, without the visual cue of the bottle or can. In an experiment that I did in a class at Stanford, 10 ...
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Why are there two formulas for the z-test?
There are two formulas commonly used in the z-test: one involving the standard error (se) and the other involving the standard deviation (std) of the population. The formulas are as follows:
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Confused about when to use z-test and p-value test for hypothesis testing
Can anyone help me solve this confusion? I don’t know why z-test and p-value test for hypothesis testing is used for this, given that the pattern between the two questions are same.
Records show that ...
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Testing homogeniety within a bin of scores given max number of bins
I have a score (ranging from 0 to 1000) which predicts a binary event. The score is based on a regression. Scores are binned. There should be a maximum of $x$ (e.g. $10$) bins. Predicitions within a ...
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At loss regarding a suitable hypothesis test for proportions in the same population
I'm dealing with a population where there are $5$ categories $A, B, C, D, E$ and I would like to make the claim that $A$ is the most common category in the population (i.e., the most frequent).
I ...
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Comparing success of group 2 and failure of group 1 (cross-tabulation comparison in contingency table)
I'm studying the endowment effect through the exchange paradigm. Participants received an object A or B. Then the experimenter asks the participants if they accept to trade their object with the ...
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Compare two proportions with a Bayesian analysis
I'm conducting an experiment in which participants receive either an object A or an object B. Next, we ask participants if they want to trade their objects with the alternative object (i.e., object B ...
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Comparing groups based on data containing proportions without raw counts
I have 2 object types, A and B
For type A, I observe delivery to demographic groups x1, x2, x3, x4.... xn.
For type B, I observe delivery to the same demographic groups x1, x2, x3, x4.... xn.
x1(a) + ...
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Comparing two proportions within contingency table for small sample size [duplicate]
I need some help for a statistical analysis.
I have the following contingency table :
I would like to compare p3 and p2, that is the comparing the proportion of event in G2 and the proportion of not-...
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Which statistical test is more suitable?
In an exam question I was asked to consider the following data related to education loan taken or not for pursuing higher education and formulate a suitable hypothesis and validate it by using an ...
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Compairing multiple distributions from repeated measures design to a refrence value
I have 24hrs of temperature measurements taken in one minute intervals for a set of individuals. Thus, there is a non-independent distribution of temperatures for each individual as each measurement ...
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Can I use the Z-Test with estimators for mean and standard deviation?
I'm trying to select feature columns in a binary classification model.
I'd like to remove near-constant columns that don't predict the target column values very well. One way of defining this is the ...
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Are large samples always needed for a Z-Test?
I have read that you should use a Z-Test when you have a sample size $ n > 30$, because this is where your sample distribution becomes normally distributed.
The Z-Test equation has more power when ...
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Can you use a Z-Test with a sample size of 1?
Background
I'm performing a feature selection process on a fraud dataset.
The dataset is made up of roughly 300 columns and 40,000 rows. It has a single binary indicator for a target.
A lot of the ...
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Significance of a single point, or population of 1
This may sound simple but I'm lost. I have a simple experiment 15 controls and 15 treatments. 13 of the 15 controls were positive, but only one of the treatment samples was positive. This makes the SD ...
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Why is the confidence interval for difference in two proportions inconsistent with the p-value for this difference in R prop.test()?
I calculated the difference in 2 proportions using the prop.test() using some exemplary data I found in internet.
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Visualizing how the 2 sample Z test works
In my stats class, we are talking about the 2 proportion $Z$-test, which compares two sample proportions. The test statistic is given as:
$$
Z = \frac{\hat{p_1}-\hat{p_2}}{\sqrt{\hat{p_c}(1-\hat{p_c})...
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Z test for paired proportions when only the two proportions are available
I am familiar with formulae for paired proportions Z test when the crosstabs table is available. However, if only the two proportions are available, I am having trouble to figure out what is the S.E. ...
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Selecting an appropriate statistical test
I have two sets of data (>10k observations), each having a binary feature describing the activity of every customer within the groups (1=active, 0=inactive).
I've seen parametric tests being used ...
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How to check normality of a binary data(True/False) for z proportion test?
One of the three conditions that should be checked before conducting two-sampled z-test for proportions is "check for normality"(link for the source: https://vitalflux.com/two-sample-z-test-...
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Z-Tests tests of Two Proportions for Continuous Data?
Why can't we do z-tests of two proportions for data from a continuous variable? For Example, if I have sample sales data (continuous, dollar) from a company and want to see if the proportion of sales ...
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Need help deciding between a T-test and a Z-test
This is the question I am working on
"Professor Liberman believes that Donald Trump repeats phrases in his speeches more than previous presidents of the United States. He counted the number of ...
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Z-test with large sample sizes but small proportions
I'm running an A/B test to determine if a change/treatment we're proposing for our website has an impact on users opting into a specific (niche) category of notifications.
To do so, I'm performing a ...
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