# Tagged Questions

A brief numerical description of a set of data.

11k views

### What are good basic statistics to use for ordinal data?

I have some ordinal data gained from survey questions. In my case they are Likert style responses (Strongly Disagree-Disagree-Neutral-Agree-Strongly Agree). In my data they are coded as 1-5. I ...
3k views

### Graphical data overview (summary) function in R

I'm sure I've come across a function like this in an R package before, but after extensive Googling I can't seem to find it anywhere. The function I'm thinking of produced a graphical summary for a ...
2k views

### Empirical Relationship Between Mean, Median and Mode

For a unimodal distribution which is moderately skewed, we have the following empirical relationship between mean, mode and median: (Mean-Mode) ~ 3(Mean-Median) Could someone please explain how the ...
9k views

### What does orthogonal mean in the context of statistics?

In other contexts, orthogonal means "at right angles" or "perpendicular". What does orthogonal mean in a statistical context? Thanks for any clarifications.
416 views

### Statistics, war stories, data intuition

I think it is fair to say statistics is an applied science so when averages and standard deviations are calculated it is because someone is looking to make some decisions based on those numbers. Part ...
391 views

### Standard measure of clumpiness?

I have a lot of data and I want to do something which seems very simple. In this large set of data, I am interested in how much a specific element clumps together. Let's say my data is an ordered set ...
10k views

### How to 'sum' a standard deviation?

I have a monthly average for a value and a standard deviation corresponding to that average. I am now computing the annual average as the sum of monthly averages, how can I represent the standard ...
1k views

### Meta-analysis in R, using metafor package

How must I syntax the rma function from metafor package in order to get results in the following real-life example of a small meta-analysis? (random-effect, ...
213 views

### Finding a comparable Control group for a treatment group?

I have a treatment group of size 30 (30 schools in California) that used a math supplemental software. In a simple analysis, I'd like to compare students' average Math growth between our treatment ...
12k views

### What is the interpretation of interquartile range?

I have daily measurements of nitrogen dioxide for one year (365 days) and the interquartile (IQR) is 24 microgram per cubic meter. What does "24" mean in this context, apart from the definition of IQR ...
266 views

### What is the meaning of $\|a\|_p=\left(\sum _{i=1}^n \left|a_i(t)\right|{}^p\right){}^{\frac{1}{p}}$?

What is the meaning of $\|a\|_p=\left(\sum _{i=1}^n \left|a_i(t)\right|{}^p\right){}^{\frac{1}{p}}$? This formula is called out on the fifth page of An Improved Data Stream Summary: The Count-Min ...
592 views

### The exact distribution of Wilcoxon rank-sum statistic U

The distribition of the rank-sum statistic U is assumed to be normal for large number of samples being considered. What is the exact distribution? I want to compare and sometimes fuse results from ...
874 views

### Command-line tool to calculate basic statistics for stream of values

Is there any command-line tool that accepts the flow of numbers (in ascii format) from standard input and gives the basic descriptive statistics for this flow, such as min, max, average, median, RMS, ...
894 views

### Alternatives to using Coefficient of Variation to summarize a set of parameter distributions?

Background I have a model with 17 parameters, and I currently use the coefficient of variation ($\text{CV}=\sigma/\mu$) to summarize the prior and posterior distributions of each parameter. All of ...
64 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 ...
109 views

### What are statistical methods for comparing different brackets

I am not particularly familiar with statistics and am looking at methods for analysing numbers that have been broken into different "brackets" or "groups" for different entities. Consider three ...
440 views

### Measure of variation around Median

Are there terms for measures of variation around the median? I know that we use "variance" for means of data but how can variance be defined for the median? Is there a similar statistic for median?
3k views

### How to generate nice summary table?

I want to have R display the data it gives me from the summary() function in a table so I can easily share this. I am currently just doing ...
105 views

### Measure of dispersion over unordered set

I'm looking for a measure of dispersion, such as standard deviation, that can be used when distributing to an unordered set. Specifically: A bucket distribution assigns a non-negative value to each ...
148 views

### Predictive model & standardized variables

In a predictive model, I have standardized variables as predictors. Say I have to rescore the model on fresh data at some point in the future: do I use the means/stds as they were when I built the ...
71 views

### Aggregating all measurements per x-value in least-square fitting

We want to select one out of a given set of (continuous) functions that best matches a set of observations $\{(s_i,c_i) \mid 1 \leq i \leq N\} \subseteq\mathbb{N} \times \mathbb{N}$ (input size and ...
901 views

### Ratio of Range to IQR vs. Coefficient of Variation — which is the more useful robust measure?

For a given set of data, spread is often calculated either as the standard deviation or as the IQR (inter-quartile range). Whereas a standard deviation is ...
240 views

### How to measure usage data across cohorts/segments?

Netflix and Google among others use customer usage (number of videos streamed or unique searches conducted) as a proxy for value, or for determining which version of a test is best. I am curious how ...
104 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 ...
584 views

### Is this the correct way to calculate $MSE$ from $SS_{\text{treatment(s)}}$, $df_{\text{treatment(s)}}$, $F$?

As described in a few of my previous questions (here and there), I am interested in deriving summary statistics from statistics reported in the literature. I would very much appreciate any advice ...
49 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 ...
2k views

### What summary statistics to use with categorical or qualitative variables?

Just to clarify, when I mean summary statistics, I refer to the Mean, Median Quartile ranges, Variance, Standard Deviation. When summarising a univariate which is categorical or qualitative, ...
262 views

### How to describe the differences in skewed data with same median but statistically different distribution?

I am comparing length of stay after laparoscopic and open appendectomy in over 160000 patients. LOS is typically a skewed variable so I use the median and interquartile range and ranksum test to ...
242 views

### How does pooling and resampling affect variance of sample mean?

Suppose I have $N$ independent random variables $X_n$. I draw a sample of predetermined size $K_n$ from each of them. Denote the average of each sample $\bar{\hat{X}}_n$, and the total number of ...
2k views

### Analyzing Likert scales

The Likert scale I am analyzing has both positive and negative questions, but all the items are answered with 4 - strongly agree, 3 - agree, 2 - disagree and 4 - strongly disagree. For analysis, ...
1k views

### What are some ways to graphically display non-normal distributions in Excel?

The ultimate goal is to show users, at a glance, if their data is normally distributed. The first attempt is a kludge that plots the data in a frequency graph. Then, the observed mean and standard ...
509 views

### Is there a way to optimize regression according to a specific criterion?

I am curious, is there a way to optimize a regression according to a specific statistic? Let's say I am interested in a model with the best possible AIC statistic (or MSE or whatever measurement I ...
52 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 ...
145 views

### Am I using the wrong statistical test?

I am using $\chi^2$ to analyze a set of data gathered over 4 time periods. The two variables are independent--each 'event' is categorized as 'good' or 'bad'. We want to prove that the intervention ...
70 views

### Use of data on a website

I wanted to use some data for statistical analysis available on a company's website. The data is in the form of a time series. Am I allowed to publish my results and conclusions?
6k views

### How to create an index

I have 5 categories, each category is divided into the subcategories low, medium and high. An object can belong to one or more of these categories with a number between 1 and 100 in each subcategory ...
74 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 ...
73 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 ...
450 views

### How to compare the variance from published summary statistics with own data?

I have compiled a very small set of summary data from the literature, and I wish to compare the variances between aspects of the literature-based data, and to some of my own data. The summary data ...
759 views

### Estimating misclassification rate from summary classification values

I'm trying to work out the misclassification rate in a published study, where the results do not include this value. However, I have the sensitivity, ...
450 views

### How do I estimate the parameters of a log-normal distribution from the sample mean and sample variance

Given the sample mean $\bar{x}$ and the sample variance $s^2$ of a random variable $X$, is it possible to estimate the shape $\sigma^2$ and log-scale $\mu$ of the log-normal distribution, with ...
46 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 ...
56 views

### How to visually show the convergence of a process?

I have some set of measurements that I have represented as vectors $x^t$ for $t \in \{ 1, 2, ...\}$. I want to test "convergence" of the process (visually) in some sense. I thought maybe I could run ...
84 views

### How to test stability/variability of statistic over time, using R

I have a long time series data (running several years). I have split the data into several series, each of 1 month duration. I then perform some custom calculations on each of the 'shortened' time ...
50 views

### What type of tool/statistic should I use to inspect two misaligned time series of different granularity?

I have two separate time series, indexed by time in nanoseconds. They both measure the same thing but because they come about in two completely different ways, the number of observations they each ...
326 views

### Visualise and interpret large set of univariate skewed data

I am trying to find out answer for this simple question. I have data (list of numbers). I have 20000 numbers. smallest number is 100 and largest is 15000. I want to interpret this data, how it is ...
568 views

### How do I calculate the range that 90% of the values fall into

Given a series of values, I know that 68% of the values fall withing one standard deviation and that 95% fall withing 2 standard deviations, but how do I calculate the range whereby 90% percent of the ...
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### A good summary measure on analyzing repeated measures of longitudinal data?

I have an interesting question on longitudinal data and I'm looking for a proper summary measure that enables me to answer my question of interest without knowing/using anything about correlated data. ...
I fit a simple linear model $y = bX$ to a data set today, and that produced 24 residuals (I have 24 data points, one for each year from 1984-2007). I would like to test the time-independence of the ...