The tag has no wiki summary.

learn more… | top users | synonyms

3
votes
1answer
68 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 "?".
0
votes
2answers
24 views

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 ...
1
vote
1answer
55 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 ...
-1
votes
1answer
44 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 ...
0
votes
1answer
47 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.
1
vote
1answer
50 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 to represent uncertainties in model parameters instead of probability distributions. I'll try to explain the motivation ...
1
vote
0answers
131 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): ...
1
vote
1answer
191 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 ...
1
vote
2answers
123 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. ...
2
votes
0answers
51 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 $\sigma(X)$
1
vote
2answers
129 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?
0
votes
0answers
27 views

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 ...
2
votes
2answers
210 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 ...
0
votes
1answer
73 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 ...
0
votes
1answer
91 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 ...
1
vote
1answer
62 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?
3
votes
1answer
120 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 ...
0
votes
0answers
54 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 ...
0
votes
1answer
178 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 ...
2
votes
1answer
103 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 ...
3
votes
2answers
98 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 ...
4
votes
1answer
119 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 ...
2
votes
1answer
508 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
votes
1answer
97 views

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.
6
votes
2answers
134 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 ...
2
votes
1answer
48 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!
2
votes
1answer
148 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 ...
0
votes
1answer
200 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 ...
1
vote
2answers
2k 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.
0
votes
0answers
28 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 ...
0
votes
0answers
80 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 ...
-1
votes
1answer
150 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 ...
2
votes
1answer
583 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: ...
2
votes
2answers
574 views

Calculating the percentage change of 2 values

If I have two different percentages and I wanted to know the change, I would simply use the percentage change formula...but what if I want to compare two percentages that have different amounts: Ex: ...
0
votes
1answer
723 views

Simple price indices question

If the inflation indices was reset to 100 in the the 3rd quarter, what would be the fourth quarter inflation index for food. I have no idea how to do this . Below is the graph: