The basic-concepts tag has no wiki summary.
2
votes
1answer
61 views
Interpretation of mean in this example
I recently presented a national test and the company in charge of preparing the test then does a standardization to provide the final scores for each person. These are the values they gave at the end ...
0
votes
1answer
39 views
Is it required for panel data to use dummy variables?
I am doing a research considering seven countries and I have panel data. My question is: do I need to include dummy variables every time I use panel data in regression, or is enough to do it as a ...
0
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0answers
13 views
Assigning weights in crowdsourcing or voting system
In Multi-weighted voting system, how is each individual worker is assigned with a weight? What is the concept behind it?
0
votes
1answer
270 views
Sampling with replacement
Suppose you have 40 different books (20 math books, 15 history books, and 5 geography
books).
Let M = math books, H = history books, G = geography books
You pick 5 books at random, with replacement, ...
4
votes
2answers
137 views
Meaning of hypothesis test for “μ = 25”; isn't it impossible?
I'm working through a stats textbook and have a question of the form:
You will perform a significance test of $H_0: μ=25$ based on an SRS of $n=25$. Assume $σ=5$.
I'm stuck on the 'equals' part ...
1
vote
2answers
79 views
Why is the Likelihood function NOT a case of the inverse fallacy?
This may be a trivial question, but as a research psychologist I do not have a robust statistics background to answer it.
It appears to me that the likelihood function--$L(\theta | \text{data}) = ...
18
votes
11answers
2k views
What is a standard deviation?
What is a standard deviation, how is it calculuated and what is its use in statistics?
5
votes
2answers
182 views
Can a sample be too large for ANOVA or a t-test?
I have close to a million data sets and whenever I run mean comparison test, either ANOVA or a t-test, I get a significance level of less than .0001 on SPSS. I'm concerned that my sample is so large ...
1
vote
1answer
29 views
Finding similar users
I am working on a problem in the online advertising space. I am trying to identify consumers similar to the set of consumers who have bought a product in the past (have 'converted'). If I can identify ...
-3
votes
1answer
61 views
Soccer contest rule puzzled me
I have a little knowledge about soccer contest rule, there is a question I cannot understand.
The dotplot below shows the numbers of goals scored by 20 teams playing in a city's high school soccer ...
6
votes
1answer
106 views
Given a historical disease incident rate of x per 100,000, what is the probability of y per 100,000?
Excuse the rather basic question, but I was reading this article on thyroid cancer in Fukushima and it was reported that 3 cases in 38,000 children were found in the previous fiscal year. Another web ...
3
votes
2answers
136 views
Scale parameters — How do they work, why are they sometimes dropped?
I'm having difficulty wrapping my head around scale parameters. How exactly do they work? Why are they sometimes ignored? (in other words, when is it important to preserve them in a calculation?)
...
0
votes
2answers
212 views
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 ...
5
votes
1answer
130 views
Conceptual distinction between heteroscedasticity and non-stationarity
I'm having trouble distinguishing between the concepts of scedasticity and stationarity. As I understand them, heteroscedasticity is differing variabilities in sub-populations and non-stationarity is ...
7
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2answers
203 views
Why are probability distributions denoted with a tilde?
What is the meaning of the tilde when specifying probability distributions? For example:
$$Z \sim \mbox{Normal}(0,1).$$
0
votes
0answers
47 views
How to assess mean estimate reliability?
Disclaimer: I am trying to fresh up my statistics from basic courses in the uni, so undeniably this is a very fundamental question, I hope you can keep that in mind in your answers.
Background: Given ...
0
votes
3answers
152 views
SPSS Interesting analysis types: Beyond the basics
Following a previous question I made I'd like to state once more that this is my first attempt at analyzing data with SPSS.
I have encoded and transformed my data properly and I also used some of the ...
1
vote
0answers
70 views
Is GLMM correct for data with several binary outcome variables per subject?
My experimental design is roughly this: I have observations of 5 categories of behavior in a specific situation, with two individuals interacting at a time. In each dyad, I only collect data from one ...
1
vote
1answer
115 views
An analytical framework for considering the geometric mean
Is there an analytical method of looking at the geometric mean that will allow one to break it down to its various components?
The focus of the question is more for financially related returns, but I ...
1
vote
1answer
46 views
How does further dividing the population increase confidence?
I am reading up on significance tests but I can't quite grasp where the "number of groups" from my example fits in.
When I ask 100 people which party they would vote for, imagine I get these results:
...
5
votes
1answer
513 views
Question about independence assumption for ANOVA, t-test, and non-parametric tests
I'm a novice in statistics and I have some confusion about the assumption of independence for statistical tests.
I searched the Internet and some information says that for the t-test, the ...
0
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4answers
364 views
Explain regression to 7 years old [closed]
Please give a clean, simple, explanatory answer that any 7 yr old can understand.
You can also link to a regression guide that is very good and simple. Should be fully explanatory all the way ...
2
votes
2answers
230 views
How does regression analysis help one understand how the typical value of the dependent variable change?
regression analysis helps one understand how the typical value of the dependent variable changes...
-- http://en.wikipedia.org/wiki/Regression_analysis
What does this mean? What "typical ...
1
vote
0answers
76 views
How to understand / visualize the error surface in online learning algorithms
I have a question about the shape of the error surface for online gradient descent algorithms. Take into account that I am trying to translate my specific question into a more general and idealized ...
-5
votes
2answers
126 views
What does regression analysis estimate Exactly? [closed]
"regression analysis estimates the conditional expectation of the dependent variable given the independent variables...."
so it's used to estimate the conditional expectation... which is basically a ...
3
votes
2answers
425 views
Does the probability of multiple independent events follow a normal distribution?
I'm heavily into role-playing systems, scripted a set of utilities in ruby for pen-and-paper games and I sort of understood statistics when I took it, but I could never for the life of me figure out ...
0
votes
2answers
602 views
Interpreting t-value as a measure of evidence
Came across an article on the web on "evaluation of training effectiveness". The author suggests that the "t-value" obtained from a "Paired t-test" conducted using pre-test and post test scores can ...
22
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3answers
3k views
Difference between standard error and standard deviation
I'm a beginner in statistics. I'm struggling to understand the difference between the standard error and the standard deviation. How are they different and why do you need to measure standard error? ...
2
votes
2answers
91 views
Sample size to tell if more than X% of the population can do <thing>
I want to perform a test to determine (with 95% confidence) whether at least 70% of a population can perform some task.
The test involves sitting a randomly chosen person down and them attempting a ...
4
votes
2answers
2k views
How should one interpret the comparison of means from different sample sizes?
Take the case of book ratings on a website. Book A is rated by 10,000 people with an average rating of 4.25 and the variance $\sigma = 0.5$. Similarly Book B is rated by 100 people and has a rating of ...
5
votes
1answer
79 views
Does it matter how you pull marbles out of this vat?
There's this large, well-mixed vat containing some unknown but finite varieties of marbles:
$$\{v_{1},v_{2},v_{3},...,v_{k}\}$$
Some varieties are more common than others.
Marbles are going to be ...
5
votes
2answers
1k views
Yates continuity correction for 2 x 2 contingency tables
I would like to gather input from people in the field about the Yates continuity correction for 2 x 2 contingency tables. The Wikipedia article mentions it may adjust too far, and is thus only used in ...
2
votes
2answers
72 views
How to detect variables discriminating a sample from the rest of the samples?
I have a traditionally structured data set where rows are observations and columns are variables. There are only a few observations but comparatively more variables. The observations are regions of a ...
0
votes
0answers
112 views
Comparing drug effects in different conditions
What is the ‘correct’ way to compare the effect of a drug in different conditions?
For example, if I have conditions a, b, c and d, where there are different numbers of ‘control’ and ‘drug’ cells in ...
4
votes
3answers
126 views
Frequentist ability to use observations
I'm not an expert in statistics, but I gather there is disagreement whether a "frequentist" or "Bayesian" interpretation of probability is the "right" one. From Wagenmakers et. al p. 183:
Consider ...
5
votes
3answers
179 views
Are these populations non-random and different?
What would be the simplest, straightest-forwardest way to determine the following:
Whether A,B,C is non-randomly distributed in each single group (IE: are there more A's in group 1 than random ...
1
vote
1answer
353 views
Basic question about cross validation
A very basic question about cross validation for Neural Networks.
Do I have to create a new network for each fold or do I have to keep the network and incrementally train it with the k-th training ...
4
votes
1answer
159 views
Problem with character vectors and linear regression in R
Quick question.
I want to perform a linear regression that looks like this:
lm(y ~ x1 + x2 + x3 + x4 +x5, mydata)
This works fine if I manually write out this ...
2
votes
2answers
406 views
Proper ways to perform time series and ARIMA
Note that I do most of my analysis using R and Excel.
Let's take this data set for example. I modified it as the data itself is proprietary: the years are also different:
...
2
votes
1answer
59 views
Likelihood of errors based on a sample
I frequently do something like: load a bunch of data, and then scan some fraction of it randomly to verify that no errors occurred. The more data I verify, the greater my certainty that no errors ...
3
votes
0answers
69 views
R: looking for “time” clusters in a data set
I am new to R and seeking some advice. I have a set (~20M) of data describing on which step a process did fail or succeeded:
...
0
votes
1answer
305 views
When can I suppress the intercept using treatreg?
Can I suppress the intercept if I know the treatment will be zero if the independent variables are zero. Also, can I suppress the intercept if I know the right hand side of the primary regression ...
4
votes
1answer
121 views
Generalization of basic probability question
This is the motivation for my question: Suppose we have $n$ tickets
in a bag, and we draw $k$ of them uniformly at random without replacement.
Now, repeat the same procedure independently (same $n$ ...
2
votes
2answers
281 views
t-test that means are the same?
I think this is simple, and I am wrong-thinking it....
t-tests are used to test the null hypothesis that the means are equal;
$H_0 : \beta_1 = \beta_2$,
$H_1 : \beta_1 \neq \beta_2$
But I want to ...
2
votes
0answers
526 views
How do I interpret this Weibull plot?
I was exploring Weibull analysis for understanding reliability of two specific specimen. I used the R package, "weibulltoolkit" and "survival" to get the plot in question. The dataset is big so I am ...
1
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0answers
92 views
Elliptic regression, basic conceptual question
I'm considering circular regression and elliptic regression on a computational and conceptual basis. If we fit an ellipse to our data then we deal with the principal components as reference for the ...
1
vote
1answer
1k views
How to compare proportions across different groups with varying population sizes?
I am trying to understand what statistical measures I can use to compare three groups having varying populations to understand which group is bad (highest probability of death or most vulnerable or ...
28
votes
7answers
3k views
If mean is so sensitive, why use it in the first place?
It is a known fact that median is resistant to outliers. If that is the case, when and why would we use the mean in the first place?
One thing I can think of perhaps is to understand the presence of ...
4
votes
2answers
9k views
Calculating the 95th percentile: Comparing normal distribution, R Quantile, and Excel approaches
I was trying to compute the 95th percentile on the following dataset. I came across a few online references of doing it.
Approach 1: Based on sample data
The first one tells me to obtain the ...
1
vote
1answer
187 views
Value based on a supplied standard-deviation
Sorry if this is a very basic question, my statistics knowledge is very low!
I've got a dataset which is basically a set of greyscale values in a greyscale texture (ie. 0-255). What I want to do is ...
