# Tagged Questions

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52 views

### plotting a factorial function in R

I have problem trying to plot the following function in R: The R code I'm using is: ...
22 views

### Comparing performance of 2 comparable tests

So I have sets of data, 15 responses for test A and 15 separate responses for test B. Tests A and B have 6 perception questions and the object is to compare the performance of representing data one ...
19 views

### How to compare 2 averages, when their sums are different

I am stuck at tring to find a convincing anwer to this question. Suppose I go a Shop A and Shop B to purchase Apples and Bananas / / Now If I calculate average Cost per Product in SHOP A = (10*10 ...
1k views

### Converting a Model from square feet to square meter

I have a simple regression fit for predicting house prices from square feet. The estimated intercept is -44850 and the estimated slope is 280.76 To make predictions for inputs in square meters, what ...
55 views

### Learning hat matrix

I'm stuck learning the hat matrix and wondered if someone could help with a question. If I have the model $$Y_i =\beta_0+\beta_1X_i+\epsilon_i,i = 1,2,3 \dots n,$$ how can I calculate the hat matrix ...
58 views

### How to write a fraction $\frac{n}{m}$ in the form $\frac{1}{x}$

If 663 million people don't have an item in the population of 7.3 billion, then 1 in how many people don't have it? What is the calculation I would use? How could I figure this problem for myself in ...
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### Statistic calculation (Conversion from one unit to another)

I could get the mean using the formulae but not the value of SD and IQR from using the formulae. What is the problem?
3k views

### Log probability vs product of probabilities

According to this wikipedia article, one can represent the product of probabilities x⋅y as -log(x) - log(y) making the ...
2k views

### What are the units of the second derivative?

Generally, what are the units of the second derivative? In this (very specific) example I have plotted height against gap probability, what should I put in place of the "?".
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### Means in R: How to find this when the exact list is not known

This is a simple question, not really related to coding but more so to some math that I am missing in my brain. I know: An object A has a length of 5 and a mean of 4. An object B has a length of 10 ...
119 views

### Probability with Z-Score

Suppose that we model the distribution of IQ scores in the general population as a normal random variable with mean 100 and standard deviation 15. Find the probability that a randomly selected person'...
163 views

### rescale a vector x to lie between arguments LOWER and UPPER in R [duplicate]

I am trying to rescales x to lie between lower and upper ...
53 views

### Maximum Likelihood Estimation Identity question

Is summation of logarithm of a random variable equal to the logarithm of the sum of the random variable.
93 views

### Reasons not to use fuzzy numbers instead of pds to represent uncertainty

Can someone explain why (if at all) it would be a bad idea to use fuzzy numbers in order to represent uncertainties in model parameters instead of probability distributions? To motivate my question - ...
213 views

### Arithmetic mean and Gini index in a grouped distribution

In the following table is represented the relative frequency distribution of 100 families related to the class of annual income (in thousands of dollars): ...
908 views

### Normalizing difference between two real values to [0,1] interval [duplicate]

If I have two positive real numbers that can take on any value between 0 and some finite real number, how do I normalized the difference between these two numbers to [0,1] interval where 0 indicates ...
312 views

### How many failed both classes

I think this might be too easy compared to other questions on this site but I really can't find the solution. ...
53 views

### Calculate $E(X)$ and $\sigma(X)$ for a simple urn problem

In a box there are 4 red and 7 green balls. A random sample of 5 of the balls is made. Let the number of red balls in the sample be $X$ (a random variable). Calculate $E(X)$ and $\sigma(X)$
2k views

### How to express the difference between two percentages?

If I have some share of a product in some sector as: 2012 2013 50% 60% and I find share change for 2012-13 then should it be 10% or 0.1?
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### How to scale a variable to a specific mean and standard deviation [duplicate]

This may be a dumb question, and I'm certain I should know this, but let's say I have one variable that has a known metric (e.g., variable A has a mean of .7 and standard deviation of .3). How do I ...
231 views

### Weird formula for linear regression

I'll try to make the matter as clear as possible given the circumstances. My boss asked me to look at an old report a former employee wrote around a couple of months ago. Apparently the report ...
97 views

### Interpretaton and Implementation of the Coefficient of Skewness

Direction: Achieve the result based on the table and its data by using Coefficient of skewness (CS). Obstacle: I have difficult to make a calculation step by step based on the equation below. I need ...
123 views

### How to calculate the weighted covariance?

I'm trying to calculate the weighted co-variance by hand to better understand what is going on. I have read the Wikipeida article and I understand the concept. However, when plugging in numerical ...
189 views

### Scale a matrix to predefined stddev and mean

Today i stumbled upon an filtering algorithm which as final step it says that it scale the output matrix so it will have the same stddev and mean as the input matrix. Is that possible?
453 views

### Performing calculation of a product of a sequence,

I have performed a calculation that a sample of records will contain at least 1 defective record assuming replacement. There are 20,000,000 records in the population, 7,000 are defective, and I will ...
85 views

### Estimating the total number of sample subsets of size 10 from a population of size 1000

If we have $n > 1000$ units to sample from, how can we estimate the number of subsets of a certain size, since the number is too much for R to handle? What I ...
1k views

### How do I transform my data so that it has mean zero and standard deviation one?

Given a series of values, 3.00,5.00,7.00,4.00,7.00,5.00,22.00,4.00,6.00,7.00,9.00,6.00,4.00 I need to 'rescale' the data so they have new values with a mean ...
133 views

### Questions on equation of log linear regression

I have been asked to check over a paper. The paper is using log linear regression. In the following log linear equation, $x$ is the dependent variable, $y$ is a continuous covariate, $z$ is a ...
155 views

### Which statistic to prove that one data point dominates the proportions in dataset?

I'm very new to statistics so apologies if this is a dumb question. I've got a grasp of the concepts but not real-life usage of them (but I am learning!). I have a skewed distribution where one ...
123 views

### Why Does This Rule Hold: $P(X>F)=1-P(X<F-1)$?

I'm studying for my first statistics exam and I've been trying to calculate $P(X>5)$ for an event which is Poisson distributed. The Poisson distribution is defined as $P(X<5)$ in table in which ...
4k views

### Converting (normalizing) very small likelihood values to probability

I am writing an algorithm where, given a model, I compute likelihoods for a list of datasets and then need to normalize (to probability) each one of the likelihood. So something like [0.00043, 0.00004,...
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### accuracy() MAPE output, is the output already in percentage form?

just curious when I get a MAPE of 10.69 from the accuracy function in SDMtools, is the output 10.96% or 1069%. This is really confusing thanks.
451 views

### Exception for sum of deviations from mean being 0

I was reading here the sum of the deviations about the mean will be 0, except for possible rounding. Could anyone explain me the what does it mean? I know about sum of deviations from mean being ...
91 views

### Unstandardized beta with an E in it

I have an unstandardized beta of -2.615-E5. What does the E mean? I have never seen this. Thanks!
862 views

### Calculating threshold turn value using mean centered quadratic terms in regression

I have a question on calculating the threshold value or value at which the quadratic relationship turns. The formula for calculating the turn is at $x = -b/2a$, following from $ax^{2}+bx+c$. My ...
478 views

### Standardizing data

I have a non-normal data set. We need to calculate the average of the numbers in this data set for planning purposes. I used “standardize” to normalize my data in Excel. Can I map the average obtained ...
12k views

### What does it mean to use a normalizing factor to “sum to unity”?

Would you also be able to provide an example? I have very little mathematical/statistical knowledge and have never understood normalization.
32 views

### a compute variable from 2 samples, what to do?

I collected 2 samples from the same 'devices' 256 of them. di and vi. I want to estimate the Population mean, which would be between 0 and 1 because I compute the variable xi from di and vi as follow:...
200 views

### Calculating demand size and intervals

could you explain how to determine a the mean and standard deviation of the following: demand size, demand interval and demand per period, with respect to minimum, 25%ile, median, 75%ile and maximum ...
153 views

### Can a percentage be lets say 0.172% even after multiplying it by 100?

Can a percentage be lets say 0.172% even after multiplying it by 100? The reason is, in my calculation i did the following; (4.3601/2329.475495)x100 giving me the above answer. Is that correct or am i ...
1k views

### What formula is needed to calculate the average adjusted gross income by zip code?

Here is an example of one zip code I'm working on: A00100 is the Adjusted Gross Income (aka AGI), agi_class is the size of the adjusted gross income. This ranges from 1 to 7: ...