# Tagged Questions

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### Difference between MANOVA and two-way ANOVA

I have read the articles of both of these statistical methods on wikipedia, and as far as I can tell they are used in the same cases. I could not tell in how far they work the same way, since the ...
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### 1 control group vs. 2 treatments: one ANOVA or two t-tests? (3 or more groups = ANOVA but explanation needed)

I have 3 groups, one control group and two treatment groups that have nothing to do with each other. I just want to see if any of those 2 treatment are different from the control group. Textbooks ...
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### Null hypothesis of t-test and ANOVA

I've recently started to brush up my statistics, and have begun doing so with two of the most often used statistical tools in my field: the t-test and ANOVA. Reading up on popular information sources ...
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### Comparing two means

I have a question on comparing means and I would be really thankful if you could help... I have a data set that contains responses from a questionnaire (so one group only, N=216). The questionnaire ...
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### How to express the difference between two percentages?

If I have some share of a product in some sector as: 2012 2013 50% 60% and I find share change for 2012-13 then should it be 10% or 0.1?
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### What is error structure?

Simple question but I can't find the answer anywhere online or in any of my texts. I think people assume you know, but I don't. What is an error structure, specifically for selecting the family ...
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### How do I determine the appropriate “weight” of a point in fantasy basketball?

For fantasy basketball, I want to quantify a player's output based on his Points, Rebounds, Assists, Steals, 3s, and Blocks production. Let's pretend that over the course of an imaginary basketball ...
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### How to calculate the p-value for a binomial test using pbinom?

25 patients receive treatment, and they each get a difference score (After-Before). 18 of them get positive scores. I would like to test the null hypothesis that p=0.5. I know that ...
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### Interpretation of descriptive statistics for dummy variable

How can I describe descriptive statistics for a dummy variable (gender of worker in a shop)? Let's say this is the info that I have: ...
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### When do we calculate the population parameter instead of sample statistics?

When do we calculate the population parameter instead of sample statistics? If there is a this kind of case which statistical tool should we use population parameter or sample statistics? A car ...
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### How to deal with non random samples?

I have a specific question about random selection, representativeness and inference. It is well known that it's necessary to use random selection to get representative samples from the population of ...
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### How to calculate the weighted covariance?

I'm trying to calculate the weighted co-variance by hand to better understand what is going on. I have read the Wikipeida article and I understand the concept. However, when plugging in numerical ...
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### How to understand the correlation coefficient formula?

Can anyone help me understand the Pearson correlation formula? the sample $r$ = the mean of the products of the standard scores of variables $X$ and $Y$. I kind of understand why they need to ...
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### Why do we need clearly defined variables as response/dependent variables?

This is not a homework question, just sort of a mental block. Why do statistical analyses require clearly defined variables as response/dependent variable? Why can't my response variable be something ...
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### Looking for a good and complete probability and statistics book

I never had the opportunity to visit a stats course from a math faculty. I am looking for a probability theory and statistics book that is complete and self-sufficient. By complete I mean that it ...
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### What type of statistics is used to describe this chart?

What kind of data analysis technique / formula would you use to describe which is the fastest OS in this chart, Windows or Linux? If Linux and Windows had equal speed on all tests, all bars would ...
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### Relationship between the range and the standard deviation

In an article I found the formula for the standard deviation of a sample size $N$ $\sigma=\frac{\overline{R}}{2.534}$ where $\overline{R}$ is the average range of subsamples (size $6$) from the ...
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### What math subjects would you suggest to prepare for data mining and machine learning?

I'm trying to put together a self-directed math curriculum to prepare for learning data mining and machine learning. This is motivated by starting Andrew Ng's machine learning class on Coursera and ...
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### Where to get started in data analysis

I wish to break into the field of data science, more specifically, analysing data sets, extracting features and classifying them or identifying relationships. However, I have no formal math ...
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### What can be concluded from small sample size?

I had just conducted a test where the customer wants to see a 20% improvement in perforation length from a baseline perforator. The baseline perforator has not been tested in the customer's specific ...
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### Interpreting F, p, & partial eta squared from an ANOVA

I am trying to interpret data from previous research and I don't understand what the individual statistics (F, p, and np2--partial eta squared) are telling me about the data, or how they relate to ...
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### Understanding how to get data from a dirichlet-multinomial distribution

I'm relatively new to Bayesian statistics and try to learn the fundamentals, maybe you can help. I have a three-sided die which produced in 100 trials: 45 times 1 10 times 2 35 times 3 I choose a ...
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### Interpreting exp(b)

With respect to (binary) logistic regression and a categorical IV, State, if a given exp(b) is .08 and I'm using indicator coding such that my reference category for the variable, State, is, say, ...
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### Why is square root taken for sample count “N” in standard deviation formula?

I'm trying to understand a very basic concept of standard deviation. From the formula $\sigma= \sqrt{ \dfrac{ \sum\limits_{i=1}^n (x_i-\mu)^2} N }$ I can't understand why should we halve the ...
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### Simple probability question

A person from group A has 20% chance of having some characteristic A person from group B has 30% chance of having the same characteristic How can I calculate the probability of a person belonging to ...