Statistical significance refers to the probability that, if, in the population from which this sample were drawn the true effect were 0 (or some hypothesized value) a test statistic as extreme or more extreme than the one gotten in the sample could have occurred.

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Multiple Linear Regression: Obtaining a Stable Model

I am working with a data set of ~1200 rows and 60 variables, and I'm trying to build a multiple linear regression model. I do this by separating 10% of the dataset to be used for validation and I use ...
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18 views

Understanding COVARIANCE when using same scale

Assuming that an experiment has 3 variables. Time, Temperature inside, Temperature outside. Also, considering that both the temperatures are measured using the same scale say Degree Celsius. If the ...
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14 views

Statistical test for power law samples

What is the t-test analog for testing against the null hypothesis that two samples come from the same distribution, if the two samples are distributed according to power law and have different number ...
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31 views

A regression specification problem: what if one control variable is a function of another—does this cause any issues?

Suppose you run a regression: $y_i = \beta_0 + \beta_1 x_{i1} + \beta_2 x_{i2} + \epsilon_i$ but you believe that: $x_{i1} = f(x_{i2})$ will this cause any issues for your estimation and ...
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10 views

How to compare a one-day count against a historic mean to identify an external change

A few months ago a client's website had some good press and their daily site visits spiked. Now, every time their traffic shows a bump, they think something external has caused it to happen. I'm ...
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460 views

About the Bonferroni correction

I have 50 variables in my dataset. I have correlated each variable against each variable, thus I have $49·50/2 = 1225$ unique correlations when no variable is tested against itself. Now, suppose I ...
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1answer
18 views

post-hoc for non homogeneous data

Which post-hoc test is used for non homogeneous data. I have checked my data set and they are normally distributes. I used Anova with Levene's test and it showed that my data is not homogeneous, and ...
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0answers
12 views

how to offer recommendation? comparison of satisfaction between two groups?

My research is "level of satisfaction in relation to customer service: comparative study between 2 fast foods my questionnaire consists of 19 questions. I'm using SERVERF, the 5 dimensions. 8 ...
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1answer
58 views

Strategy for Analyzing Data

I have been learning about Machine Learning (via Udacity) and Statistics (via Coursera) the past few months and trying to figure out a good way to combine them for a general approach to explaining ...
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25 views

1-way and 2-way ANOVA giving wildly different results

I'm hoping someone can help me understand this. I'm using sigmastat 10. My data consists of multiple outcomes (2 continuous and 2 count) belonging to 3 groups (test/sham/naive). If I perform a 1-way ...
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2answers
74 views

data analysis, dissertation of thesis? help please?

I'm having a problem with my dissertation. My research is "level of satisfaction in relation to customer service: comparative study between 2 fast foods my questionnaire consists of 19 questions. ...
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1answer
22 views

testing significance from a non-normal simulated distribution with CIs

Say we have a value B =-0.9631366 of a population level parameter from a real population. Then we use simulations based on some mechanistic knowledge of the ...
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4answers
72 views

Coefficient changes sign when adding a variable in logistic regression

In my logistic regression the sign of coefficients of a variable (location distance of an amenity) changes based on other variables (with time -ve, with travel distance +ve) in the model. When the ...
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1answer
50 views

What am I missing in basic OLS? [closed]

I must first admit that I haven't done stats in a loooong time, but I need to do some rudimentary analyses. My issue is that my findings just don't "look right," so I want to see if anyone can spot ...
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0answers
38 views

Dichotomizing Continuous Variables in Regression: Good or Bad?

I believe Dichotomizing(also called bucketing/binning) of continuous variable is not always a good idea. My colleague while building regression model always bins continuous variables and only keep ...
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1answer
11 views

Comparing accuracy of answers to a question to expected accuracy by chance - statistically significant?

I'm sure this is a very simple one, but I'm struggling to find an explanation online for something so simple. I have a survey with 38 respondents. Each one has answered a multiple choice question ...
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27 views

Assessing Significance of Graph Statistics for a Selection of Vertices in a Network

I am dealing with the following problem: Assume $G(V,E)$ being an underlying network and $M_1$, $M_2$ sets of disjoint subsets of $V$ (e.g. if $|M_1| = k$, $M_1 = \{U_1,U_2,\dots,U_k\}$, ...
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29 views

Compare $R^2$ statistical significance in multivariate multiple regression

I have a multivariate multiple regression model with 3 dependent variables and the same 5 covariates. I used manova and mvreg in ...
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31 views

Check significance of correlation for non-normal data and small sample size

I need to check the significance of the correlation between a model output and observations. This is a complex vegetation fire model, and I'm aggregating its outputs regionally to get total burned ...
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7 views

Further analysis for significance at three points in time, 1 group, 2 questions

The only information that I have is that each person completes a survey comparing job satisfaction and level of stress (higher scores represent higher satisfaction and stress) at 3 months, 6 months, ...
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36 views

Statistical significance test: One way Anova and Kruskal-Wallis test

I was comparing data between two groups and for each group there was six samples. My data are as follows: group 1: 103.56, 103.32, 103.32, 104.27, 103.56, 103.8 group 2: 97.16, 97.16, 96.69, 98.58, ...
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1answer
13 views

Two-stage cluster sampling problem

I'm having difficulty understanding the following problem. It seems like it is a two stage cluster sampling problem, but then the defective red lightbulbs make the question even more difficult. I'd ...
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1answer
26 views

Survey data: finding the most significant predictors?

I have about 5,000 responses to a survey in which users were asked how strongly they agreed with a statement on a 5-point Likert scale. This response is my dependent variable - I want to find out what ...
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3 views

How to test data migration quality on very large sample set

I am migrating 2M individual bio-specimens from one IT application to another (sample location data, 5 levels). While the data migration tools are "validated", I want to create a statistical model to ...
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1answer
69 views

Questions regarding Binary Logistic Regression

I am very new to statistics and is currently performing binary logistic regression analysis to test null hypothesis for my dissertation. First, both my independent variables and dependent variable ...
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6 views

how do I test the relationship between infection and nurse:patient ratio

I am evaluating whether the prevalence of a specific infection in the ICU bears a relationship to the nurse:patient ratio over time. The infections are whole numbers (nominal variable)and the nurse: ...
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86 views

OLS vs IV estimates - Sign and Significance

Assume I have an equation with 1 endogenous variable, and many other exogenous variables. Also assume I have 2 valid instruments for the endogenous variable for IV estimation. If I were to estimate ...
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18 views

test to show statsticial change due to an intervention

I have a group of 222 test results that were reviewed separately by two interpreters X and Y. Based on their assessment, they were to assign management into 4 categories A, B, C and D. Then another ...
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1answer
29 views

Running many $t$-tests to find the most significant way to divide a dataset

I apologize for my stats illiteracy in advance–I'm not a stats guru by any stretch, but am trying to learn. To start, I'll just introduce what my data set looks like, then what I'd like to ...
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1answer
67 views

LR test on marginal effect

Say I have the following regression model: $$\text{Wage}_i = constant + α·\text{YearsOfEduc}_i + β·\text{Age}_i + γ·\text{CompletedHighSchool}_i + \mbox{δ·$\text{NumOfSiblings}_i$} + ...
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1answer
38 views

Wald test on marginal effect

Say I have the following regression equation: $$Wage_i = YearsOfEduc_i + Age_i + NumOfSiblings_i + u_i$$ How would I go about peforming a wald test of the hypothesis that for an individual with ...
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13 views

Benchmarking Software Exercises

I am building a website for practicing programming in various languages. The content is user driven; some users write exercises with test frameworks for validating solutions, and other users write ...
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9 views

Significance test for longer pronounciation

I have a set of words spoken by a group of native speakers and a group of non-native speakers. In each record I determined the length of the burst (a phonetic term). I believe non-native speakers tend ...
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23 views

Best size for control in Control/A/B/C/D split test

I'm doing some split testing on a website, and have multiple tests running along with a control. Say we have control/A/B/C/D. If we only had control/A, then I know I should make them both the same ...
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33 views

Determine if regression results are significantly better with method A or method B

I'm working on a regression case and I am using two methods, lets say method A and B. Due to the randomness in the optimisation techniques of these methods the output will always differ slightly. ...
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311 views

Bias in jury selection?

A friend is representing a client on appeal, after a criminal trial in which it appears that jury selection was racially biased. The jury pool consisted of 30 people, in 4 racial groups. The ...
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1answer
38 views

How should I interpret a factor that is significant both (1) in linear form in interaction with another factor and (2) in its quadratic form?

Our study aims to identify and understand how several ecological factors relate to parasite abundance in a colonial animal. However, we are uncertain on how to interpret a factor (density) that is ...
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1answer
10 views

What's the right test to use to find significance in a table of incidence rates?

I have some data about conversion rates on different browsers, as follows. ...
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16 views

Sample of one, extermination of fruit flies and daily life challenges

First of all, I'm very well aware that a sample of one is ridiculous in any normal scenario in the domain of statistics, and I know that any rationale from this would probably only have esoteric ...
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1answer
42 views

What statistic to use

My 8 year old daughter is conducting an experiment to assess memory. She has 3 groups. Condition 1, Condition 2 and ...
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28 views

Testing of sensitivity for different algorithms

I have some queries I would like to discuss, I am doing some analysis for sensitivity. I am not from the field of statistics. I work with RNA-Seq data. The thing is I have found some genes which are ...
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2answers
17 views

Calculating chi-squared values for percentages?

I'm using scipy and I'd like to calculate the chi-squared value of a contingency table of percentages. This is my table, it's of relapse rates. I'd like to know if there are values that are ...
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4 views

How to compare series of foreclosure rates wrt to time and place

I have three categories of foreclosure rates in NYC (rates are number of foreclosures per 1000 homes). The three categories are: overall rates of foreclosure, rates for homes within a flood zone, and ...
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0answers
23 views

Visualise significant differences in a contingency table?

I'm working with pandas and scipy, and I would like to find a quick way to visualise unusual values in a contingency table. Say this is my contingency table: ...
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2answers
33 views

Pearson correlation test for non-gaussian data

I want to perform significance test for correlation coefficient. However my data is not normally distributed. In my books I have found tests only for the normally distributed data. Is there such test ...
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1answer
1k views

Could it be shown statistically that cars are used as murder weapons?

I heard a story recently in which someone said if they wanted to kill somebody (and get away with it) they would do it with their car. They cited various statistics about the number of auto-related ...
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20 views

which statistical significance to rely on?

Hello, I'm trying to estimate the relationship between oil price and gdp. My question is should I test for statistical significance for each estimator or should I test the statistical significance ...
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0answers
19 views

Statistical test for cumulative curves

I have three treatment groups represented in three cumulative curves. What is the best test to show differences among them.Knowing that treatments were observed cumulatively for only seven days.
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13 views

Test for pairs of small integers

I have two classifiers, say $A$ and $B$ and I am performing 10$\times$10-fold cross-validation on them and record the number of instances correctly classified from the test set. Unfortunately, the ...
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Consistent Questionnaire Responses

I want to ask please questionnaire responses in Likert Scale. I have got some respondents who had consistent answers for a large number of questions. For example, over 75% or 80% answers (in different ...