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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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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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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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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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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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? ...
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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 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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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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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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What is the reason in R prop.test() for 2 proportions to report Wald's confidence interval yet Rao test score? They are not consistent [duplicate]
I calculated the difference in 2 proportions using the prop.test() using some exemplary data I found in internet.
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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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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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Can we use z-test when the population standard deviation is known but the sample size < 30?
Let's say I know the population standard deviation, but the sample size is small (≤30). Can I use the z-test? The reason I ask is that I see two different statements.
We can use the z-test, if we ...
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Is a t-test applicable here in comparing two proportions?
I have 3 categories of tissues examined by microscopy (A , B and C, 12 of each). I want to test whether the proportion of tissues staining by a particular dye, differs in the three categories. Each ...
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Why is t-test more appropriate than z-test for non-normal data?
(Disclaimer: I am aware that some form of this question has been asked many times on this site, e.g. this, this and this - I was hoping to find a definitive answer to this from Google but I am still ...
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A/B Testing Question - Power Analysis for Two Proportion Z Test
I'm having a hard time wrapping my head around experiment design and what appears to be a disconnect to experiment outcome analysis.
If I am proposing a z test of two independent proportions (...
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Contradictory results while performing Z-test
Hello Everyone,
I'm relatively new to statistics and this community so please bear with me and forgive me if I commit any mistake while asking my question. For starters, here are two hypotheses tests ...
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Comparing two classifiers with two proportion ztest by using balanced accuracy
I'm looking for statistical differences between two classifiers by applying the two proportion z-test formula to them and then performing the hypothesis test.
If p1 and p2 are the balanced accuracy ...
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Why are ztest and chisquared test not returning equivalent sample size results?
I'm using the statistical software G*Power to find the minimum sample size needed to detect whether or not the difference in two proportions is statistically significant in an AB test I'm setting up. ...
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What are the distribution values (mu, sigma) for alternative hypothesis of differences between two proportions? How to calculate?
When comparing two independent proportions (p2, p1) in an A/B test, null hypothesis states that the difference is 0, while the alternative hypothesis states it is something other than 0, let's say mu1....
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Minimum sample size calculations for two-sample two-tailed proportion z test
I'm struggling to reconcile some minimum sample size calculations. I'm seeking a minimum sample size for two-sample two-tailed proportion z test. I set my parameters as follow...
alpha = 0.05
power = ...
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Finding statistical significance difference using Z score test using r
I wonder how to perform the z proportion test to check which COG category of Shewanella_sp_Alg231_23 is significantly high p (<0.05) from other genomes. To undersatnd I have attached a bar braph.
<...
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Testing if the difference of the sum of two distributions is significative
I have two distributions and I wish to understand if the difference of the sum of the elements sampled from these distributions is significative or not.
I have set the problem this way:
I have $n_{x}$ ...
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Interpreting coeftest results; z-test; t-test, unfamiliar with the output
I am using coeftest to run z- and t- tests on a few different pieces of data. The output comes in this form:
fit <- lm(dest_flood ~ type_flag, data = runsample)
coeftest(fit)
...
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McNemar test or Two proportion z-test?
Consider an experiment where a group of 200 people were asked before and after what is their preference, with possible outcomes being A and B. The research question is:
Is there a difference between ...
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Power analysis of group proportions when sample sizes cannot be guaranteed to be equal
I have a new UX feature, which I need to test out on users on a social media platform. When a user creates a post, he/she can add hashtags to gain community traction. As owners of the platform, we ...
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Two Sample Independent Test for Proportions (z test or t test)
Context:
I have two independent samples that I want to compare for equality through an AB test.
The metric being evaluated is binary: user clicks or not (proportions).
Question:
I keep reading that z ...
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Using a z-test for proportion in place of Chi-Square
Here's the study:
Pam knows from prior research that children who are seated in a room with 4 doors are equally likely to pick any door when asked which door they would choose then leaving the room. ...
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Hypothesis testing for ordinal proportions for multiple independent subjects divided between two groups
I have two biological groups - each with multiple subjects (7 in one and 10 in another). Each subject provides 40-80 observations, which can be classified into either of two ordinal categories. I have ...
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