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0answers
13 views

Counting the number of combinations from 5 equals sets

I have 5 sets with three elements each: A can be either 2,1 or 0 B can be either 2,1 or 0 . . E can be either 2,1 or 0 You can only pick one element from one of ...
1
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1answer
31 views

Need help calculating number of possible passwords with given criteria

I need help calculating the number of possible passwords with a given set of criteria. Here is the set of criteria: Passwords are case insensitive. Must be 6-14 characters. Must contain at least 1 ...
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0answers
7 views

Combining two time-dependent statistical distributions

I've got a bit of an interesting statistical conundrum. I've got a time-dependent process that I've been able to model as the combination of two different distributions. Let's imagine that I'm ...
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0answers
34 views

How to calculate the Variance of a linear combination with dependent sums and products?

For my research it is necessary to calculate the significance of the following coefficients: a1=b1+b2+(b7+b8)*W a2=b3+b4+b5+(b9+b10+b11)*W a3=b1-b2+(b7-b8)*W a4=b3-b4+b5+(b9-b10+b11)*W. They are ...
4
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1answer
73 views

How many ways there are to add up 7 numbers to sum of 180?

Farmer has 7 pigs and 180 potatoes. How many combinations of distributing those 180 potatoes there are? Order does not matter. Each pig can get from zero to 180 potatoes, but all 7 pigs must get ...
3
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1answer
49 views

Exactly 1 pair in 3 random cards from a poker deck

poker deck is 13 rank (2-Ace) and 4 suits for a total of 52 cards Draw 3 random cards what is the chance of exactly 1 pair (same rank)? using combination $$\frac { \binom{4}{2} \binom{13}{1} ...
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0answers
21 views

Interpretation when Linear Combination of Coefficients in linear regression is not significant

I have a linear regression (OLS) and was told that I could use Linear Combination of Coefficients (lincom with Stata) to analyze the influence of those variables. Unfortunately, my stat skills are not ...
2
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1answer
57 views

Addition of two estimated means to become new estimated mean

In order to estimate population mean there were conducted two independent questionnaire survey. They have mean estimates $\hat \mu_1$ and $\hat \mu_2$ respective. And their standart deviations are ...
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0answers
15 views

Combining the standard errors of Cohen's Kappa computed for multiple rater pairs

In a study on intra-rater agreement with 8 raters, I have computed Cohen's Kappa for each of the raters and I estimated the standard error of each of the kappa values using the Jackknife method. To ...
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0answers
22 views

Why do we use combinations rather than permutations when calculating sample points

Let me state a question to use as an example: Suppose I have 3 blue marbles and 4 red marbles. Suppose we take 5 marbles from this without replacement. What would be the pdf of the random variable Y ...
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0answers
15 views

Merging quality parameters into one

I am analyzing data from an OPC server that logs process parameters including three quality parameters. These three quality parameters together determine the overall quality of the output. Therefore, ...
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0answers
17 views

SVM kernels combination

Let's suppose we have classification problem with two classes. $$X^l = (x_i, y_i)_{i=1}^l, Y=\{+1, -1\}\;\; y:X\rightarrow Y$$ $$x_i \in R^n, y_i = y(x_i),\;\; i = 1\dots n$$ One of the most spread ...
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0answers
19 views

Should I be using the Combination interpretation or the Permutation interpretation? [duplicate]

Question: A family has three children but you don’t know their sexes. If at least two are boys, what’s the probability one child is a girl (assuming that all outcomes are equally likely)? My Answers ...
1
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1answer
23 views

Given a set of bounded integers; find number combinations which sums to S

Consider that I am given a set of $n$ integers $a_1, a_2, \ldots a_n$, which can take any value in the interval $1\leq a_i\leq t$, where $t$ is a positive integer, how can I find the number of ...
0
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0answers
24 views

How to represent the sum of two linear model predictions in same unit

I have built two linear regressions independently of one another, and $Y_1$ and $Y_2$ are in the same units. I am interested in using the sum of $\widehat{Y}_1$ + $\widehat{Y}_2$ (the predictions) to ...
0
votes
1answer
96 views

Poker chance of straight or 8 outer straight draw on the flop from suited connectors 34 - TJ

Poker - 52 cards 4 suits of 13 (rank) cards each Poker probability Rank - ace (1) is both high and low so A23456789TJQKA Suited - Holding 2 cards of the same suit Connectors - 2 sequential ...
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0answers
75 views

Combining n simultaneously occuring probabilities of an event occuring into one summative probability

I am a bit lost with regards to the problem described a bit further down, because though many methods to approach it are documented in available literature, the verdict as to which model is the most ...
0
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1answer
58 views

Combining two probability scores [duplicate]

This question is rather mathematic, and I am quite sure some theory should already exist but I can not find it... Say I have some data records, and for a certain record X two independent statistical ...
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0answers
29 views

State of the art for bagging/model averaging? [closed]

If I estimate a collection of models predicting $Y$ by $\hat{Y}$, which methods are out there to combine these forecasts? Which methods work well/best (and why?) to improve prediction accuracy? My ...
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2answers
49 views

Probability that 2 out of 3 friends win a raffle?

Let's say it's me and 2 other friends are at a raffle. There are 10 total participants. 3 of the 10 of us will win something, I don't care about what we win. A person can't win more than once. What is ...
3
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2answers
62 views

How many combinations of K ordered numbers from N numbers list

I have N numbers, 1-N (my N is 70). I need to know how many combinations of sequences of K numbers (K is 8 in my case) are possible, where the sequence is always increasing. Examples: ...
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0answers
24 views

How to add time estimates

Imagine I have a bunch at tasks to complete sequentially. There is some uncertainty about how long each task will take to complete. So for each task, we might estimate a 50% chance that it can be ...
0
votes
2answers
44 views

Variance of Gaussian linear combination

I have two independent gaussian distributions to combine and I have a doubt. Let's say we have $X \sim N(\mu_x,\sigma^2_x)$ and $Y \sim N(\mu_y,\sigma^2_y)$. I want to mix the two variables with a ...
0
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0answers
21 views

Sampling combinations

I'm running a simulation where the different inputs are combinations of $n$ values taken in $r$. The problem is that even though $n$ is small, the number of different combinations is very large, so I ...
1
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1answer
132 views

minimizing total travel time [closed]

Green circles are salesman and A-B-C are destination points. I need to move green circles so that total travelled time should be minimum and each salesman should go to a different point. So ideal ...
0
votes
1answer
23 views

Unique vectors that can result from bootstrapping

My question concerns the unique number of vectors that can result from bootstrapping. Ie I have a vector of length 12 with the following elements : 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1 and I would like to ...
5
votes
1answer
110 views

The “strongest password”

I have an app which is protected by a four-digit-PIN and the user got five attempts at logging in before the account is locked. Now, one of my customers wants to "strengthen" the security and ...
0
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1answer
84 views

Tricky Question re Customer Purchase Probabilities

I would like to calculate some parameters relating to customer purchasing in a retail situation. I have some basic information which I can use: Customer visit frequency in the form of probability ...
1
vote
1answer
105 views

Which is the maximum number of combinations between two populations

I have two populations of size N1 and N2: pop1 = {a,b,c,d,e,f,g} and pop2 = {h,i,j,k,l} I want to produce combinations of this two populations swapping individuals between the two but keeping the ...
0
votes
0answers
20 views

How Can I Combine Multinomial Data from Survey with Two Parameter Univariate Distribution

I have survey data, $X$ that measures a variable on a 1-5 Likert type-scale. I have a second variable $Z$ which, given a suitable parametric assumption, I can identify the mean and the variance but ...
2
votes
1answer
150 views

Combining multiple outcomes in studies (no meta-analysis)

I'm looking for a way to combine effect sizes (mean difference) and variances for several single studies but I don't want to conduct an overall meta-analysis. That means I'm only looking for an ...
0
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0answers
13 views

How to calculate the total forecasted demand after forecasting demand of two types of clients seperately

I am trying to make a sales forecast with the ARIMA model. This business has two types of clients that have completely different buying behaviour. My idea was to separate them and make a sales ...
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3answers
339 views

What are the statistical methods I can use to find popular or common combinations of categorical variables?

I am doing a study on polydrug use. I have a data sets of 400 drug addicts, who each stated the drugs that they abuse. There are more than 10 drugs and hence there large possible combinations. I have ...
3
votes
1answer
62 views

Calculate the probability of observing n elements in m draws from an uneven frequency distribution, in order but consecutive or not

I want to calculate the probability to observe a certain sequence of n elements in order, but not necessarily consecutively, after drawing m times from an uneven frequency distribution. For example: ...
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0answers
16 views

Basic question about assigning items to groups

Suppose there are 9 items, which are assigned to three groups. The first group may contain 2 items, the second 3, and the last one 4. In how many different ways the items may be assigned to the ...
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0answers
32 views

Combining Forecasts: Best Information to Solicit from Forecasters?

Suppose Statistician $m=1$ produces a set of $h$-step-ahead point forecasts $\hat{x}_{t+h|t, 1}$ of $x_{t+h}$ where $x_{t+h} \in [0,1]$. Also, this point forecast could come with: a predictive ...
0
votes
1answer
39 views

Deck of Cards - Combination Question

The question asks to randomly draw 13 cards from a standard deck (52 cards). What is the probability that there are 3 aces in those 13 cards you drew. Let $n(s)$ be the number of $13$ card ...
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4answers
2k views

Variance of linear combinations of correlated random variables

I understand the proof that $$(aX+bY) = a^2Var(X) +b^2Var(Y) + 2abCov(X,Y), $$ but I don't understand how to prove the generalization to arbitrary linear combinations. Let $a_i$ be scalars for ...
0
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1answer
35 views

Combining unbiased hit rates

I am analysing data on an emotion perception task, where participants must decide if a given face is happy, sad, angry or fearful (essentially a forced choice between 4 options). I am confident that ...
3
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1answer
103 views

How to combine data several studies with events?

I have a compilation of following data on 10 studies, all of which had 2 groups: a control group which received usual treatment and an active group which received an intervention. The subjects were ...
0
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1answer
37 views

Arranging numbers

I keep on having problems with the same kind of questions involving combinatorics. This is one such problem where I am stuck. A bag contains 9 discs labelled 1 to 9. Andy chooses 4 discs at ...
3
votes
1answer
499 views

PCA: Eigenvectors of opposite sign and all eigenvectors are zero in R

I'm learning PCA in R language. I met two problems right now that I don't understand. 1) I am performing a PCA analysis in R on a 318×17 dataset using some custom code. I take eigen function in R ...
5
votes
1answer
190 views

Number of combinations with elements from different sets

Unfortunately I could neither find nor develop a closed formula, but I believe there is a simple solution for this problem. Could you please help me? Suppose that there are 4 different sets: Set A, ...
1
vote
1answer
278 views

Combination of two SVM Kernels

According to the book "Support Vector Machines" from Cristianini and Shawe-Taylor, it is feasible to make kernels from kernels. My question is now more in application of this methods with tools like ...
2
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0answers
39 views

Total probability distribution of multiple random lotteries

My question: Imagine $d$ identical lotteries. Each individual lottery picks a cost $c_{i}$ between $0$ and $1$. Picking a costs occurs with probability distribution $f(c)$. The total cost of these ...
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0answers
16 views

Combinations conceptual confusion

Suppose we toss a fair coin 43 times. What is the number of cases where number of heads > number of tails? I'm doing this like this: we'll have a satisfactory case only when number of heads are 22, ...
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1answer
38 views

What is the meaning of averaging combinations of independent random variables?

I'm getting into the management of multiple independent random variables in determining expectation and variance, but cannot see where averaging of a linear combination of independent random variables ...
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0answers
183 views

Probability of selecting exactly 2 members of a group of 7, out of 35 people, if 3 people are picked

There are 7 friends A, B, C, D, E, F, and G that belong to a classroom of 35 students. Three students are chosen from the 35. What the probability that exactly two of the group of friends is chosen? ...
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0answers
19 views

How many different arrangements, when selecting 2 out of 5 objects? [closed]

How many different arrangements are there, when selecting 2 out of 5 objects? In this question what should I use - nPr or nCr?
10
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2answers
1k views

Roll a 6-sided die until the total $\geq M$. Mean amount by which $M$ is exceeded?

Here is the question: You roll a fair 6-sided dice iteratively until the sum of the dice rolls is greater than or equal to M. What is the mean and standard deviation of the sum minus M when M=300? ...