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0answers
10 views

Permutation and combination [on hold]

You are at an ice cream shop that offers 9 different flavors of ice cream. A large ice cream cone comes with three scoops of ice cream. You can choose an ice cream cone with any combination of flavors ...
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3answers
213 views

Number of combinations for a 4- digit code lock [closed]

Your suitcase has 4-digit code lock. You forgot the code, but you do remember that the sum of first two digits was equal to the sum of two second digits. How many combinations do you need to check in ...
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1answer
46 views

Does combining forecast models produce good prediction intervals?

In this blog post, @rob-hyndman says: If you only want point forecasts, that is the best approach available in the forecast package. It is also better than any of the commercial software (at least ...
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1answer
40 views

Basic Proability Doubt

I have a basic probability doubt. If I have 5 different vehicles backstage, out of which 3 random can be showcased to the public. What is the probability of each vehicle to get to showcase? Once a ...
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1answer
23 views

How are the outcomes that generated from different predictive models combined to get more accurate predictions?

The simple average is commonly used to combine the predictions of different predictive models. Apart form the simple average, what are the other methods that can be used for combining the predictive ...
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0answers
9 views

Which test to use for associations between 2 IV (nominal+continuous) and 1 DV (continuous)?

I have two independent variables, one of which is in nominal scale (binary), while the second is continuous. I want to determine whether any of the combinations of the two are associated with a change ...
2
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0answers
39 views

Combining data in the same study

I have identified 17 studies for use in a meta-analysis. In order to make sure that I analyze the data correctly, I had a couple of questions regarding how to approach two of them. First, one ...
2
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0answers
102 views

How to find the maximum number of independent pairwise comparisons between groups

I have the following situation: Consider a dataset that is comprised of a number of factor levels x = gl(5,1) > [1] 1 2 3 4 5 > Levels: 1 2 3 4 5 I want to ...
2
votes
2answers
81 views

Covariance matrix for a linear combination of correlated Gaussian random variables

Supposing $X$ and $Y$ are random variables with a joint bivariate normal distribution and covariance matrix $\Sigma_{XY}$. Consider the following linear combination for constants $A$, $B$ and $C$: $$...
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2answers
28 views

Pemutations and combinations problem

I have this one question in statistics: There are five women and six men in a group. From this group a committee of 4 is to be chosen. In how many ways can the committee be formed if the committee is ...
3
votes
1answer
36 views

Alternating random number sequence combination [closed]

I have a problem that I have a hard time figuring out. We have a sequence of 10 numbers, 0 to 9. We want to find all the combinations where, when choosing from the sequence 18 times with replacement, ...
0
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1answer
20 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 ...
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1answer
33 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
11 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
37 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 ...
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1answer
93 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
votes
1answer
51 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
34 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
64 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
21 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
27 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
17 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
18 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
vote
1answer
26 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 ...
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0answers
26 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
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1answer
121 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 (e....
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0answers
78 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
votes
1answer
96 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 ...
3
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0answers
36 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 ...
1
vote
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
84 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: 1,6,23,45,51,...
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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
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2answers
53 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....
0
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0answers
26 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
138 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
122 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
votes
1answer
113 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
113 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
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0answers
24 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
201 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
15 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
374 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
64 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: ...
0
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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 groups?...
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0answers
34 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
46 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 ...
1
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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 $i\...
0
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1answer
36 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 ...