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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Best statistical method to show different performance week over week

I am trying to get best statical method to show performance of accumulative revenue by customer compare week over week. Currently I have about over 100 customer charts compare by hour from same day ...
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12 views

Statistical Significance of Turnaround Time

My laboratory recently implemented MALDI-TOF MS for identification of gram negative rods in blood cultures. I collected data retrospectively from laboratory reports comparing the time from isolation ...
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2answers
19 views

paired-sample t-test

I have taken weight measurements before and after a treatment. When I run a paired sample t-test and if there is a significant change, would it be possible to make the claim "95% of the time ...
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5 views

Statistical comparison of 2 dependent cohen's ds

How would I statistically test the significane of the difference between two Cohen's d derived from different tests within the same sample? Specifically, in my neuroimaging data metabolism in brain ...
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22 views

Statistical Test for Two-Alternative Forced Choice Task (2AFC)

I conducted a learning experiment and assessed whether participants learned with a two-alternative forced choice (2AFC) task consisting of 100 items (25 items of category 1, 25 of category 2, items of ...
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28 views

Statistical significance to a population

I have a question in regards to statistically significant sample sizes to a population. I am working with data in excel and wanting to put the formula for this into the workbook as well but have run ...
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7 views

Test(s) For Comparing qPCR results / ΔΔCт values

To be clear, I'm talking about real-time polmerase chain reaction (qPCR), not Principle Component Regression. Though from a company selling qPCR reagents, here is a good walk-through of the ...
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20 views

How to CORRECT un-reliable and un-stability in the prediction results

Currently, I meet such questions when building Random Forest model using my data set. My full data set: X_lab: 839 * 469 and y_lab: 839 * 1 which is for all labelled data and X_unl: 20346 * 469 which ...
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12 views

regarding the statistics to test the impact of some subset values on a given variable

For a given variable, there is a set of values. We know that these values can belong to different clusters. For instance, a lot of values center around a small value while other values center around a ...
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33 views

How to ReSample the Training DataSet

I have a training dataset which differs significantly on several parameters (t-test/f-test) with the test set (for which the labels are not known to me.). I am thinking of re-sampling from the ...
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11 views

Conditions on ratio of $\frac{\sigma_{BIB}^2}{\sigma_{RB}^2}$

I'm attempting to solve a question about the variances of random block design versus balanced incomplete block design. I feel I am close to having an answer, but I'm not quite there yet. Question: ...
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1answer
16 views

Exploring Diffrences and Agreement with Wilcoxon and Kendall - both tests show significant findings

I calculated a Wilcoxon Signed Rank Test to investigate differences between a pair of dependend variables. Also I conducted a Kendall's tau-b on the same variables. Surprisingly both tests get ...
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1answer
23 views

How to present statistical significance results among more than two datasets?

Let us say that we have 5 sets of data: $$ a = (a_1, a_2, \dots, a_{10}) \\ b = (b_1, b_2, \dots, b_{10}) \\ c = (c_1, c_2, \dots, c_{10}) \\ d = (d_1, d_2, \dots, d_{10}) \\ e = (e_1, e_2, \dots, ...
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13 views

Is it Complete or Partial mediation? Or no mediation at all?

Kindly explain the given situation, is it partial, complete, or no mediation at all?
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1answer
20 views

Finding Bias$(s^2)$ in incorrect linear model

I am unable to find the bias of the sample variance estimator in this problem. Unfortunately I keep coming up with Question: Suppose that the true linear model is $y = X_1\beta_1 + X_2\beta_2 + ...
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6 views

How can I calculate the statistical significance for two different proportions of the sample? [duplicate]

I provided two English sentences for the same group of students to judge as grammatical or ungrammatical. 70% of the students judged the first sentence as grammatical whereas only 37% of the same ...
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1answer
40 views

Standardized regression coefficients

I have a question regarding standardized regression coefficients and the correlation matrix. I have a two part problem that I am working on, and I need to show that the correlation matrix R is equal ...
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15 views

Statistical significance of differences between percentages

I have a problem annoying me. I have associative word lists which formed by 150 participant's answers to given word. At the same time, i gathered information about word's valance with a 5 point Likert ...
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1answer
41 views

statistical hypotheses

A company that packages peanuts states that at a maximum 6% of the peanut shells contain no nuts. At random, 300 peanuts were selected and 21 of them were empty.With a significance level of 1%, can ...
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26 views

A/B/C Testing - Aggregate data for comparison?

Let's say I have 3 ads: A, B and C. These ads perform as follows- ...
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28 views

Certainty estimate for prediction of largest of several converging variables

Problem I want to have an estimate for the certainty which of several (3-4) variables is the variable with the largest value, given some sample values which should eventually converge to different ...
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34 views

Jonckheere-Terpstra Trend Test Use and Effect Size

I would like to find out if there is a statistically significant increase among four groups. I have 4 ordinal groups (ex group 1 is count 1-20, group 2 is count 21-30 etc) and I have data for each of ...
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53 views

Show alias coefficient of Plackett Burman design equals $r_{ij}=\frac{c_{1i}'c_{2j}}{N}$

Consider a Plackett Burman design with N rows and let $\beta_{1}$ be the of the regression coefficients corresponding to the main effects and let $\beta_{2}$ be the vector of the regression coefficients ...
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10 views

M statistic and software ProtoArray Prospector

I would like to reproduce the statistical result in this paper: http://www.ncbi.nlm.nih.gov/pubmed/24947363 They said "the M-statistic test in ProtoArray Prospector was applied to the normalized ...
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31 views

Monte Carlo test for spatio-temporal randomness

I have a collection of discrete spatio-temporal observations $d(x,y,z,t)$ on the surface of a sphere. The data is sparse and is in the order of ~100 points, but there is a bimodal clustering of these ...
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42 views

Multiple Regression - Residual Analysis

I am doing a multiple regression analysis regressing GPA against several 0/1 indicator variables (representing course completions). My fitted vs. residual plot is biased and looks awful. See below. Is ...
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180 views

How to interpret variables that are excluded from or included in the lasso model?

I got from other posts that one cannot attribute 'importance' or 'significance' to predictor variables that enter a lasso model because calculating those variables' p-values or standard deviations is ...
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59 views

If $\frac{(2n-1)s^2}{\sigma^2} \overset{}{\sim} \chi^2_{2n-1}$, can I take the variance of both sides to get an equality relation?

I currently have a standard result regarding variances and it looks like: $\frac{(2n-1)s^2}{\sigma^2} \overset{}{\sim} \chi^2_{2n-1}$ that is, it is approximately a chi-squared distribution with ...
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2answers
70 views

Proper Statistical Test for Binary Data

I looking for the best statistical test to apply in a particular situation and I hope I can find here the answer(s) I'm looking for. First of all some details: I'm studying 33 different mutants of a ...
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12 views

Three stage cluster sampling

I was just curious if anyone knew where to find information on three-stage cluster sampling. There is a significant amount of information on two-stage cluster sampling, but I am unable to find ...
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23 views

How to calculate sample size for poll / ranking

Let's suppose there are Y options to choose from. I'd like to run an experiment with a sample of n participants (from a larger population), each will choose 1 option from the Y alternative according ...
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77 views

Estimating the uncertainty of a bias and a scatter

I have one single set of observational data. Assuming I know the right answer for one property of this data set and then I use one tool to measure this quantity. To get an estimate of the amount of ...
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44 views

What constitutes a significant drop in speed of vehicles on a 40mph road?

A friend had an incident near where he lives recently that is similar to my line of work (currently) that made me think what constitutes a significant drop in speed as a result of a change in road ...
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27 views

What kind of test is this?

I have a client that wants to test 3 pricing options to visitors of a website. All options are for the same product and service (no difference except pricing). Their current idea is to present all 3 ...
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1answer
39 views

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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2answers
26 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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1answer
25 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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48 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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18 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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4answers
536 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
21 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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13 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
72 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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26 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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89 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
24 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
88 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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45 views

Dichotomizing Continuous Variables in Regression: Good or Bad? [duplicate]

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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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 ...