# All Questions

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24 views

### Determining suitable seed number in R to randomly split data into training and test sets

Good day. I have sample size of 160 and I am randomly splitting them into 70% train and 30% test data sets. My question is about the set.seed() value which returns different random samples in each ...
20 views

### Does heteroskedasticity matter when estimating a regression using the entire population?

The F-statistic, t-statistics, p-values and standard errors of the estimated coefficients will all be incorrect in the presence of heteroskedasticity. However, does this even matter if I am working ...
40 views

### AB testing and hypothesis testing

I have an entire market for which I plan to run two offers. I randomly split the market 50/50. All of Group A receives offer 1 and all of group B receives offer 2. I want to compare proportions of ...
26 views

### Conclusion for not rejecting a null hypothesis

I'm actually quite confused what is the outcome we could deduce here for the other exercise types listed in the diagram. From my interpretation, the null-hypothesis is: There is no association ...
32 views

### compute sample probabilities given a poisson distribution

I have read through a large number of stack posts about hypothesis testing on Poisson distributions. Some examples: Calculating test statistic of a poisson distribution Hypothesis testing with ...
34 views

### Significance Test with dichotomous variable

I have a set of data. The data contains 30.000 observations of a set of several variables. One of those variables indicates a nominal segment classification. In total there are six different segments. ...
10 views

### Location level a/b testing sample size

We are setting up experiments to measure impact on the city level. Customer in certain cities are treated and we have list of holdout cities with similar behavior. Measurement of lift of the ...
19 views

### Calculating probability of voting results from small sample aize

2 million people voted in a poll for their favourite song. 35,000 votes have been counted so far, of which: 575 votes are for Song A 466 votes are for Song B 393 votes are for Song C (And the ...
14 views

### How tailed area decided for hypothesis testing?

I have a doubt in basic hypothesis testing. Suppose I have a testing setup as below. I have assumed null hypothesis that my sampling distribution has $\mu = 60$, and I get a sample set with sample ...
49 views

### Hypothesis testing on subsamples and cross validation

When working on very large datasets, identifying effects rests more on quantification than significance and many questions/answers give insight on what to do regarding large samples like this (very ...
815 views

### Why do several (if not all) parametric hypothesis tests assume random sampling?

Tests like Z, t, and several others assume that the data is based on a random sampling. Why? Suppose that I'm doing experimental research, where I care much more for the internal validity than the ...
497 views

### Significance of relationship between sex and bachelor's degree or higher (2017 U.S. labor force, ages 25 and up) (disparity, difference)

Reports and webpages like the following prompted this question: "Women Now at the Head of the Class, Lead Men in College Attainment" by Kurt Bauman and Camille Ryan, October 7, 2015, United States ...
57 views

### mean of sample vs the sample mean

Say I have a sample population A it has mean $\mu_A$. I sample A and obtain another sample population $\hat A$, it has a mean of $\mu_\hat A$. If a hypothesis test indicates that I should be 95% ...
11 views

### Is it Acceptable to Sum Multiple Observations for Proportion in Inferential Statistics and Hypothesis Testing?

Suppose I'm sampling two groups for an experimental research where I'm measuring how people respond to a certain type of question under the interference of certain factors in one of the groups, and ...
49 views

### An Elementary Question on Sampling

(Apologies if the question is too basic or vague. I have taken only one course in the subject long ago. This question stems from a silly argument I was having with a friend) Two friends want to find ...
122 views

### A/B test and SRS

I was reading about Simple Random Sampling (SRS) from this lecture notes. It says that SRS, which actually is a sampling without replacement makes $x_i$ not independent. Then I thought about A/B ...
293 views

### Using binomial vs central limit theorem in hypothesis testing

This is the question that I was working on: "An airline claims that the proportion of luggage that is lost is less than or equal to 0.06. A random sample of size 200 is taken. Out of the 200 ...
39 views

### Long-run behavior of p-values? (simulation) [duplicate]

I was wondering why the expected value (i.e., long-run average) of the p-values from a simulation of a binomial experiment in the below experiment becomes roughly about $.61$, regardless of $p$; the ...
63 views

### Testing count post sampling

Some automated sampling is done (by a computer) on a collection of $N$ identical items. The sampling process consists in keeping each item with a constant probability $\alpha$ and discarding it with a ...
20 views

### Determining Regions of Rejection: Why does optional stopping affect null hypothesis testing?

I'm having great difficulty understanding how selecting a stopping point alters the sampling space in the example below. Specifically, why is the probability of 5 successes and one failure different (...
7k views

### Sample Size proportion per control vs. experiment group

I am taking an online statistics course and I understand how to calculate the necessary sample size for a hypothesis test. I am using an online calculator like http://www.evanmiller.org/ab-testing/...
44 views

### Replication of a normally distributed variable

Suppose we know there is a True Effect size = + 0.2 for an experiment. Now, suppose that I want to find out what happens if I repeat the exact same experiment 10,000 times. If I believe such ...
472 views

### Difference in proportions with finite population

I'm looking for a suitable test for the difference in two proportions when dealing with finite populations. The standard z-test seems to only apply to infinite populations, so you lose some power. It ...
282 views

### How are the null distributions created for hypothesis testing?

I'm struggling to connect the idea of a sampling distribution of a test statistic to the null distribution. If I run many simple linear regressions on samples extracted from a population of data I ...
61 views

### Is it possible to formulate a null hypothesis for this single-sample case?

I have the percentage of completed activities of a set of users that have used a concrete application. I have the number for each of them, for instance: Participant #1 --> 0.85 Participant #2 --> 0....
297 views

### Unknown process outputs binary results, how to prove that this process is (or not) a Bernoulli trial

I have an unknown process that produces binary results. I am trying to determine if this process is a Bernoulli trial. From wikipedia: In the theory of probability and statistics, a Bernoulli ...
57 views

### Testing a hypothesis about the size of coefficients in a linear relationship

In the project, I was asked to determine whether $0.5(\text{Father's Height} + \text{Mother's Height}) +6.5$ correctly predicts the height for boys. To do this, I've collected 50 male students' ...
69 views

### Is controlling for cluster good enough in an analysis with a clustered sample?

I'm trying to understand how sampling design affects analyses and I'm a little confused about how to adjust for clustering. From what I've read, when you have a clustered sample you are supposed to ...
44 views

### Determine significance of an observed continuous distribution given many randomly generated continuous distributions

Suppose there is a vector, v, that contains the body height of every person over 30 years old on earth. It looks something like this: ...
70 views

### Test fitness proportionate selection algorithm implementation

I implemented a couple of algorithms for fitness proportionate selection (roulette-wheel, alias method and roulette-wheel via stochastic acceptance) and now I want to write a test to ensure that ...
45 views

### Distinguishing two Bernoulli random sources

I have a source of independent Bernoulli random variables, which is either $(X_i)$ or $(Y_i)$ where $\Pr[X_i=1]=p$ and $\Pr[Y_i=1]=q$. I can sample as many values as I'd like, and would like to figure ...
614 views

### Joint inclusion probability for Horvitz–Thompson estimator

There is a Wikipedia page for the Horvitz–Thompson estimator. It is an estimator for the population total. Unfortunately the page has failed to state the standard error. From here, the standard ...