Tagged Questions
0
votes
2answers
32 views
Quadratic and geometric average
I'd like to find the find the quadratic average and the geometric average. To do this I have these informations :
The standart deviation, the arithmetic average and the number of values.
I know the ...
0
votes
0answers
78 views
Standard deviation of the weighted mean
How do you find the standard deviation of the weighted mean?
The weighted mean is defined: $\bar{x} = \frac{\sum{wx}}{\sum{w}}$
The weighted standard deviation (since it is not specified, I take it ...
0
votes
2answers
91 views
Average percentage of percentage
I ran a survey on my website where users marked a checkbox for what % they did X. Something like this.
...
1
vote
1answer
26 views
Generating statistics from data samples, that are of snapshots.
My question is part math part computers but I need more of the math answer then a computer answer. I am going to be grabing snapshots of a moment of time on how a computer is performing. Because of ...
1
vote
1answer
45 views
Estimating a sample mean using sub-sample means
we collect a lot of data on a daily basis via an API, and part of this data includes fields that represent sample means. Specifically, we get provided with a sample mean and the sample size, lets call ...
1
vote
1answer
238 views
Average proportion for proportions with different denominators
Say I have an experiment in which subjects are asked to respond to some stimulus. Their responses are transcribed and coded, first as "Valid/Invalid", and then for the valid responses, ...
1
vote
1answer
754 views
Average, standard deviation and min/max values
I'm analzying a computer science paper and just found in the experimental setup the following statement:
Average (standard deviation) of number of files per peer: 464 (554)
Min - max number of files ...
1
vote
2answers
69 views
Finding one value from a mean.
7 boys have a mean height of 1.80m.
Peter joins the boys and now the mean height is 1.75m.
Find Peter's height.
0
votes
1answer
68 views
Continuously sampled event: Estimating the value of a future data point, based on past measurements and their tendency
Problem
I'd appreciate some ideas on how to define a formula to estimate the value of a future data point for a continuously sampled event, based on past measurements and their tendency.
At any ...
0
votes
1answer
58 views
How to calculate variance on spending?
My maths is a little rusty, but I understand how to calculate variance in general. A colleague asked me if I knew how to calculate the percentage variance on budget spending.
Given this example:
...
0
votes
1answer
58 views
Algorithm to Get a Product score based on rating
I am trying to device a algo for product score. Here are the inputs
User rates a product on 5 different criteria out of 10
Each criteria has a different weightage with all adding up to 100%
There ...
1
vote
0answers
42 views
Taking averages
Suppose I have a function $f(\theta)$ that is a function of the angle $\theta\in [0,2\pi)$.
Why is the average of $f$ over a large collection of randomly oriented objects:
$$\int f(\theta)\sin ...
2
votes
2answers
60 views
Calculating statistic for multiple runs
I have s imple, general question regarding calculating statistic for N runs of the same experiment. Suppose I would like to calculate mean of values returned by some Test. Each run of the test ...
1
vote
0answers
21 views
Dynamic Light Scattering
In DLS does the combination of the Time Average and Ensemble Average give a better statistical average than the results shown by each case considered separately ?
1
vote
1answer
82 views
How long does it take to complete a sticker album?
We are collecing stickers in chocolate bars and whenever we open a bar we get a random new sticker. There are many different stickers and we try to collect them all.
We open the first bar and get a ...
0
votes
1answer
652 views
Weighted average vs. weighted mean
Is there a formal difference between weighted average and weighted mean?
I get corrected to the latter if I type in the former in wikipedia, and then there is a lot of stuff about the name "average" ...
1
vote
1answer
87 views
Determining the error from a list of individual errors
I have a list of values each with a corresponding error. I can determine the average/mean of the list, but I'm not sure how to best calculate the error over the entire population.
e.g.
...
0
votes
2answers
303 views
Weighted average of two frequencies
This should be really simple but I'm getting stuck and I'm probably extremely dumb..
I know that a machine receives two kind of parts:
Type 1 -> with frequency 50 per week, each one is processed for ...
2
votes
1answer
156 views
Remove statistical outliers
I've analysed newspapers by counting the language distributions of the articles.
The results look like that:
...
2
votes
1answer
158 views
Calculating kWh from multiple watt readings
I have a file which contains watt readings for various times throughout the day. A reading is stored roughly every 6 seconds.
...
1
vote
1answer
75 views
changing values in a distribution without changing the average
I have a set of positive values and I need to increase or decrease this set by adding or reducing number of values. But I would like the mean of values is not altered much.
Example:
I have this array ...
6
votes
1answer
2k views
Average percent increase not equal to total percent increase?
I tried searching around for this but it was difficult to boil down the search terms. Plus nothing seemed to be showing up anyway.
What's an easy way to show that the average percentage increase of n ...
2
votes
0answers
198 views
How can I compare two averages of imperfect measurements, with their std. deviations?
I have a process by which I measure the times it take to do something, (run some code), and this time varies, a lot. I'm trying to optimize this code, making small changes that sometimes have small ...
0
votes
1answer
84 views
Calculate average time
I have a huge list of times and would like to calculate an average or typical time. If I would just use the median (or other "normal" types of calculating an average), for example 23:59 and 00:01 ...
0
votes
2answers
94 views
How to compute 2 grades, one statistical (IRT) and other normal, together, to make a fair average? [closed]
An exam is composed of 2 tests. The first test's grade is fixed at 500 plus or minus 100 for each standard deviation obtained, calculated by computer using the Item Response Theory. The second test ...
3
votes
2answers
151 views
Course Grade - Statistics Question
I'm confused about finding the standard deviation of various weighted objects in a problem. For example, consider an academic setting, with four assessments as follows:
...
0
votes
1answer
105 views
Getting Average
How excatly do I calculate the average? Can somebody explain step by step process of how to get an average?
If I have an array of numbers (5, 3, 4, 3, 1) and so on. And I need to get the average of ...
5
votes
4answers
759 views
How can I calculate “most popular” more accurately?
I'm developing a website at the moment.
The website allows users to "rate" a post from 0 to 5.
Posts can then be displayed in order of popularity.
At the moment, my method of calculation is pretty ...
1
vote
2answers
932 views
What is the standard error of the mean of an exponential distribution of the form $Ae^{Bx}$ with N measurements?
What is the standard error of the mean of an exponential distribution of the form $Ae^{Bx}$ with $N$ measurements?
3
votes
1answer
756 views
leading and lagging moving average indicator
What are leading short and lagging long moving average indicators and how do we calculate them?
e.g. for the following data set, and let window size be 2. Can you ...
1
vote
1answer
1k views
Proving correlation coefficient = 1 or -1 given X and Y=a + bX
Given $X$ and $Y = a+bX$, I have to prove that:
If $b \lt 0$, then $\rho = -1$. If $b \gt 0$, then $\rho = 1$.
I've gotten to the point where I have:
$$ \rho = \frac{b \cdot \sigma_x }{ ...
2
votes
3answers
171 views
Average amount of money received from pulling three random coins
Let's say I have a bag of coins, which contains 1 quarter, 2 dimes, 3 nickles and 4 pennies. If I were to randomly pull out 3 coins, on average, how much money would I get?
4
votes
2answers
578 views
Why is median age a better statistic than mean age?
If you look at Wolfram Alpha
or this Wikipedia page List of countries by median age
Clearly median seems to be the statistic of choice when it comes to ages.
I am not able to explain to myself ...
