A brief numerical description of a set of data.

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1
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3answers
21 views

Standard deviation of the mean? [duplicate]

I don't think I understand how you can have a standard deviation of a mean σx̅. x̅ is all the sum of all values divided by the sample size n. It's a single value. How can there be a standard ...
0
votes
1answer
18 views

How to determine probability of score when selecting from pool of values?

The question seems simple but I just can't solve it. I have twelve test scores and three are to be picked at random to determine the overall test grade. How can I calculate the probability of my ...
1
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2answers
50 views

Homoscedastic and heteroscedastic data and regression models

How to understand the homoscedasticity and heteroscedasticity in context of regression models? Is there a way to check these properties in R?
0
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0answers
12 views

What is the individual's ID in the 1994 Peru LSMS dataset?

I had a quick question about the Peru LSMS from 1994 (http://microdata.worldbank.org/index.php/catalog/617). The LSMS is split up into several dozen files, all of which contain different pieces of ...
2
votes
0answers
80 views

I have a problem with bayes and train lines

I have this problem which I can't fully understand it: Assume you have entered in a foreign city of unknown size. At entrance you see a tramcar with number $100$. Let us assume that the tramcar ...
5
votes
0answers
86 views

If the distribution is bimodal, does p-value mean anything?

P-value is defined the probability of obtaining a test-statistic at least as extreme as what is observed, assuming null-hypothesis is true. In other words, $$P( X \ge t | H_0 )$$ But what if the ...
3
votes
1answer
31 views

What is the interval that relates to the mean as the equal tailed interval relates to the median and the highest density interval relates to the mode?

When summarizing a one dimensional continuous distribution (e.g. a posterior distribution) it is common to use either an equal tailed interval (aka quantile-based) or a highest density interval. The ...
0
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0answers
28 views

Regression Puzzle GLS var/covar matrix of B given summary statistics

There is a problem posted back in 2009 that I found that has me puzzled. I believe the estimates are from a generalized linear regression because after some thought it seems $X'X$ is impossible to ...
0
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0answers
20 views

Cox regression with interaction giving NA values, how to interpret? + Choosing covariates based on p-values

I am working with a dataset with 12 covariates(categorical). The covariates have different Levels, some are from 0-5, and one has as much as 0-11 categories. I started with a univariate analysis to ...
8
votes
2answers
317 views

Is variation the same as variance?

This is my first question on Cross Validated here, so please help me out even if it seems trivial :-) First of all, the question might be an outcome of language differences or perhaps me having real ...
1
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0answers
23 views

Limitations of using interpolated data

I have a data set that is composed of point locations in a landscape, lets call this dataset X. Some of the points in data set X need to be grouped together because they "function" together as a ...
4
votes
2answers
93 views

Does the slope of a regression between observed and predicted values always equal the $R^2$ of the original model?

As the title to my question says, I am confused as to when the $R^2$ of a model fit does not equal the slope of the regression between observed and predicted values. I am trying to present model ...
-4
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3answers
74 views

Null Hypothesis [closed]

A survey found that 70% of college professors believe that their online education courses are as good as or superior to courses that use traditional face-to face instruction. What is the null ...
2
votes
0answers
28 views

Markov chain and process

This is not homework. Just practicing for an upcoming exam. Question is taken from a web pdf : http://www.dartmouth.edu/~chance/teaching_aids/books_articles/probability_book/Chapter11.pdf Consider ...
0
votes
0answers
28 views

How to measure the randomness of a time series?

I have at least two time series. How can I measure which one of them is more random than the others? I am also interested in monitoring the changes in the amount of randomness over time for an ...
0
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0answers
16 views

variance, standard deviation and standard error [duplicate]

When describing the variance of a sample data set, we can use variance and standard deviation. ...
0
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0answers
25 views

Cumulative standard deviation calculation

I have a calculated daily survival probability, and associated SE. From this I can obtain the standard deviation. I have to report the cumulative survival over a specific period. So for example, for a ...
12
votes
2answers
1k views

Pizza statistics for the masses

A short entry on the NY Times website provides the Facts and Figures of pizza consumption in the United States. I have a casual interest in how statistics are used (or abused) to provide information ...
0
votes
0answers
14 views

Is k-th difference method suitable for making the data stationary?

I have a huge data set which is non-stationary. (Checked non-stationarity with unit root test). I'm wondering how can I make my data stationary. I need stationary series because I want do some ...
0
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2answers
98 views

Logit-link GLM Summary Interpretation

I made a logit link, GLM model with 7 explanatory variables. How do I interpret the coefficients and CI? ...
0
votes
1answer
69 views
2
votes
1answer
103 views

Youtube 301 views. Whats Statistical about it?

Apparently any new video on YouTube seems to freeze at 301 views for a period of time before the actual views start reflecting. The reason seems to be that youtube during this time "figures" out if ...
0
votes
1answer
61 views

How can I compare variables with uneven data sets?

I'm doing a stationary sport in which I use different colored equipment for different weather. I am recording my scores along with the color of the equipment and the weather in which I am using it. I ...
0
votes
0answers
14 views

What are the most accurate athletic performance indicators based on scores?

I want to generate statistics for a sport I'm doing. I am collecting data such as my scores and instances in which I miss. Based on this, I calculated averages for my overall performance and for when ...
4
votes
2answers
73 views

Do M-estimators and L-estimators overlap?

In my self-study, I have read the wikipedia entries and some books in regards to M-estimators and L-estimators. I understand that M-estimators are so called "M" because they "Maximize" the likelihood ...
0
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0answers
51 views

I do not understand the terminology of $Q_n$

I am trying to understand what looks to be some simple terminology issue, involving $Q_n$ from my book here: Specifically, I do not understand what they mean when they say $m = {n \choose 2}$, and ...
0
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0answers
13 views

getting the variance of a set composed of a group of subsets [duplicate]

I have a data set $\mathcal{S}$, which is composed of several subset as $\mathcal{S}=\{S_1,...S_i,...S_n\}$ Each $S_i$ has its own mean $\mu_i$, variance $\sigma_i$, and size $\|S_i\|$. Is there a ...
0
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0answers
29 views

Why is the scatter diagram always symmetric around the SD line?

This may seem like a dumb/vague question. When you draw a line of slope $\frac{\sigma_y}{\sigma_x}$, why is this line the major axis of the scatter-diagram ellipse? Is this some property of the ...
1
vote
2answers
49 views

What is the best method of performing a chi-squared test with only one set of data?

I am trying to perform a chi-squared test on the following data: Achieved: 31 Expected: 19.87179 From a total of: 182 Is it possible to perform such a test on just one item of data like this? All ...
0
votes
0answers
10 views

What is the meaning of Mean Sq for for quantitative variables in AOV?

In an open course, Mean Sq was explained using a factor variable. Suppose your linear model is y = b0 + b1*I{x == A} + b2*I{x == B} where A, B are Factor ...
0
votes
1answer
34 views

Experimental design type?

A pencil depth tester is used for various pieces of paper. Two different pencils are used. The class measures how deep the pencils go into the various pieces of paper. Paper Pencil Depth ...
0
votes
0answers
35 views

Average difference in averages and t-test

I'm currently working with some individual level data and have run up against a wall in figuring out the best way to analyse it. Let me describe: We have a sample of N=9000 Physicians. For each ...
4
votes
1answer
59 views

Is there a statement for the median like the central limit theorem for the mean? [duplicate]

According to the Central Limit Theorem (CLT) in statistics, the distribution of the average of randomly sampled n observations tends to follow normal distribution as the sampling size n becomes ...
0
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0answers
92 views

Categorical Dependent Variable in R

How does one interpret the beta coefficients in R for a model that has a categorical dependent variable that is not binary? For instance, in the hypothetical model below, I would interpret B1 as being ...
1
vote
1answer
212 views

kurtosis, positive skewed and negative skewed for probability distribution

When discussing probability distribution, I always read something such as excess kurtosis, positive kurtosis, positive skewed and negative skewed. What exactly do these concepts indicate? In practical ...
0
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0answers
28 views

Combining the Counts and P-Values

I have experimental and computational data for n genes in data matrix. The rows are the genes and columns are its values. Now, the data is from two sources: Computational Prediction Results in form ...
2
votes
0answers
45 views

Unpaired t-test with only summary means

Is it appropriate to conduct an unpaired t-test with only summary means from both groups? For example, let's say you want to compare: a. Professor A's scores received on a evaluation by his ...
1
vote
2answers
417 views

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: ...
1
vote
0answers
83 views

Non-parametric z-score for comparison of outliers/extreme values across set of non-normal distributions

I have a network and for each node in the network I am calculating a certain property, essentially its 'connectedness' to a set of source nodes. In order to identify nodes which are better connected ...
4
votes
3answers
121 views

How to measure student skill level based on a set of questions answered at different points in time and of different difficulties levels?

I am working on an e-learning system with a friend for our final year (Computer Science) project which is part of the under-graduate programs mandatory 'courses'. I have a question about making ...
0
votes
0answers
118 views

Formula to calculate variance for the sampling distribution of sample statistics (i.e. sample mean, sample median, and sample proportion)

What would the formula to calculate variance for the sampling distribution of sample statistics (i.e. sample mean, sample median, and sample proportion) be? At first I thought it would just be the ...
3
votes
1answer
120 views

Compare two independent variables

I have two variables, one containing project delivery rates for a particular language, and the second containing team size that worked on these projects. I am particularly new to statistics and I want ...
1
vote
0answers
30 views

Explaining the difference between error propagation and “grand variance”?

I have the following data concerned with simple radiation detection. I collect a background dose $B$ for 100 seconds and find the standard deviation and get the uncertainty $E_B$. I then take 10 ...
3
votes
0answers
55 views

What is the analysis techniques for comparing two sets of ratings

Say, I have collected 50 comments. For each comment, I am planning to get 10 ratings from non-expert raters for the following criteria: "interesting vs. not interesting". Based on the plurality of ...
0
votes
0answers
54 views

A concise way to describe the distribution of words in a text

I have a text, and I count, for each distinct word, the number of times that word appears in the text. In some texts, there are many rare words, so the distribution will have a long "tail" of words ...
1
vote
0answers
58 views

Measure for temporal “spread”

I basically have a timespan from January until August (or any other timespan) which is divided into active periods (denoted by a red line in the plot) and inactive periods (the rest). What I want to ...
3
votes
1answer
56 views

The X quantile of the difference between two RV's

To first provide some context, I have two boxplots (displaying median, 25th, and 75th percentiles), and I'm wondering what a boxplot of the difference between these two boxplots would look like. The ...
-1
votes
1answer
54 views

Should I always order the data vector in ascending order before using “summary” function in R? [closed]

Should I always order the data vector in ascending order before using summary function in R? Or should I just apply summary ...
3
votes
1answer
79 views

Mining survey data to discover high and low performing cohorts

I'm analyzing datasets of users that range in size from 5,000 users up beyond 150,000 users, and each of these users have at least 32 data-points (sometimes more, sometimes a few less) with (about) 5 ...
5
votes
1answer
67 views

Is the chance of independent events just summed, when calculating overall chances of any event?

I'm not a mathematician or statistician (my last exposure was over 30 years ago with stats classes in school). My problem is if events are independent do you just add them together to get the overall ...