The sum of several numbers divided by their count nicely summarizes the overall size of the numbers involved in a single value.

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2
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3answers
48 views

The mean of the of a sum is the sum of the means

Transcription: The mean has good mathematical properties. The mean of a sum is the sum of the means. For example, if $y$ is total income, $u$ is "earned income" (wages and salaries), $v$ is "...
1
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1answer
484 views

problem in understanding overall change in average

The average weight of 5 men is decreased by 3kg when one of them weighing 150kg is replaced by another person. This new person is again replaced by another person whose weight is 30 kg lower than the ...
-3
votes
1answer
18 views

Quantitative Aptitude Average [on hold]

The average weight of a group of boys and girl is $38$ kg. The average weight of boys is $42$ kg and that of girls is $33$ Kg. If the number of boys is 25, then the number of girls is?
1
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0answers
10 views

Does Averaging the score from correlation across multiple variables yield a more accurate correlation score?

This may be a beginner question but I am making a application which I using to do correlation research to be used in financial markets. The application pulls in different data sources and compares ...
5
votes
2answers
444 views

Find the average value of the function…

Find the average value of the function $$F(x) = \int_x^1 \sin(t^2) \, dt$$ on $[0,1]$. I know the average value of a function $f(x)$ on $[a,b]$ is $f_\text{avg}=\dfrac1{b-a} \int_a^b f(x) \, dx$, ...
-1
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0answers
29 views

What are greatest and least average values? [closed]

I'm working on a school assignment in which I've a series and I've to compute these two values, but I can not find the meaning of these terms. I tried searching online resources but wasn't able to ...
3
votes
4answers
149 views

Removing my averages

thanks for your time and apologies if this is far too simple for this group. I am trying to remove my average from a total average. Meaning: The total average for a subset of data is 55. I am 29% ...
-2
votes
0answers
34 views

Describe the behavior of the average temperature difference of Earth as a function of time. [closed]

So I am having trouble with this question for my ENVS class. I am not sure what type of formula to use or where to start, in no way or form does my professor give an example in our notes. Here is the ...
0
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0answers
22 views

Aproximation for the variance (sum)

Given that we know The mean of a population $\tilde W(t) = \sum_{i=1}^{n}f_{i}(t)*W_{i}$ The variance of the population in the previous step $Var(0) = \sum_{i=1}^{n}f_{i}(0)*(W_{i}-\tilde W(0) )$ ...
0
votes
1answer
19 views

Find upper bound from average value

I have been give a function, its average value, and the lower bound of an interval, I am trying to find the upper bound but I am a bit lost on how to do that. Here is what I have so far: $$ f(x)= \...
1
vote
2answers
380 views

Aggregating standard deviation to a summary point

I have a range of data (server performance statistics) is formatted as follows, for each server: ...
0
votes
1answer
11 views

achievability of average

Out of a textbook. Informally, the goal is to show that if from a given set of values ($2^n$ many values) in the range of $[0,m]$ (for fixed $m,k$), more than half are less than $m\cdot (1-\frac{1}{2^...
-1
votes
1answer
28 views

Average distance (maximum norm) from origin to the nearer of two random points in a unit square

I got a unit square, the origin (0,0) and two random points which are uniformly distributed on the 1x1 unit square. What is the average distance in maximum norm from origin to the nearer of the two ...
1
vote
1answer
61 views

2 trams are coming every 5 and 10 minutes. On average, how long do I have to wait for any tram to come?

I want to follow the approach from Christian Blatter here 3 trams are coming every 10, 15 and 15 minutes. On average, how long do I have to wait for any tram to come? using "the assumption that the ...
0
votes
3answers
47 views

What is the relationship between average distance between 2 random points in a cube, with min and max?

I wrote a computer program to simulate the minimum, average, and maximum distance between $2$ random points in a unit length cube (such as $1$ cubic foot). The minimum possible distance is $0$ and ...
7
votes
8answers
2k views

3 trams are coming every 10, 15 and 15 minutes. On average, how long do I have to wait for any tram to come?

3 trams are coming to the stop every 10, 15 and 15 minutes. On average, how long do I have to wait for any tram to come? It's a practical problem, not some kind of a riddle for which I have a ...
1
vote
1answer
422 views

Calculating average customer turnover

I am currently coding a script which displays data for a company intranet. I am stuck with a question that seemed pretty simple, but turned out to give me headaches. We have the following scenario: ...
0
votes
2answers
23 views

Trying to Calculate Averages for Record Types

I am trying to compute the averages for the following (3) types of records but not sure if I am getting the correct results: 387 Total record count (valid/invalid/other) - created by 45 total users ...
6
votes
7answers
49k views

Sum of averages vs average of sums

I have essentially a table of numbers -- a time series of measurements. Each row in the table has 5 values for the 5 different categories, and a sum row for the total of all categories. If I take ...
0
votes
2answers
30 views

Find the average when zero is also there [closed]

If a set $A = \{0,1,10\}$ . What is the average? Is it $\frac{(0+1+10)}{3}$ or $\frac{(1+10)}{2}$.
0
votes
1answer
101 views

SAT Math Question Confusion

I was doing a practice new SAT Test and was wondering exactly what this question is asking and how it got to the answer. Thanks!
43
votes
3answers
75k views

Why is an average of an average usually incorrect?

Can someone explain why taking an average of an average usually results in a wrong answer? Is there ever a case where the average of the average can be used correctly? As an example, let's say ...
2
votes
2answers
24k views

What is the difference between the normal average and weighted average?

What is the difference?For what kind of purpose do we use the weighted average method?Why don't we instead always use the normal average method?and also,how to get the weighted average of some numbers?...
27
votes
4answers
11k views

Incremental averageing

Is there a way to incrementally calculate (or estimate) the average of a vector (a set of numbers) without knowing their count in advance? For example you have ...
3
votes
3answers
3k views

what does `ensemble average` mean?

I'm studying this paper and somewhere in the conclusion part is written: "Since this rotation of the coherency matrix is carried out based on the ensemble average of polarimetric scattering ...
1
vote
1answer
35 views

Which is the proper way to calculate average speed.

Let's say we have a graph, a distance-time graph, and there are couple points on the graph. The points are connected to each other with different slopes, so with different speeds between the points. ...
0
votes
1answer
24 views

Detecting unusual activity

How would one go about detecting unusual order flow in an intelligent way. That's very broad, so let me narrow it down. I have a trading system with clients entering number of orders every day. At ...
0
votes
1answer
12 views

Calculating the average with Limited memory and without using the count

I am having a flow of numbers on an embedded device, and I cannot store the flow of numbers and would like to calculate the average. I have checked around and found one way was to do like this Avg= (...
6
votes
4answers
16k views

what is the difference between average and expected value?

I have been going through the definition of expected value in Wikipedia (http://en.wikipedia.org/wiki/Expected_value) beneath all that jargon it seems that the expected value of a distribution is the ...
5
votes
1answer
235 views

Prove that if 2000 m is run in 4:50, then one mile is run under 4:00

Prove that if 2000 m is run in 4:50, then one continuous mile is run under 4:00. I was thinking -- yeah, this follows easily from the other question, where I asked that if 2 miles are run in 7:...
0
votes
0answers
8 views

Weighted mean / average where you reward the lowest value - cost - distance

Best I've several weather-station (200), placed across the country (508 municipalities). Now, I would like to prescribe the weather info, e.g. temperature, to each of the municipalities of that ...
1
vote
0answers
30 views

What do attendance figures tell me about regularity? What does the average tell me about individual attendance?

Suppose I have a group of $N$ people, attending a series of $M$ events, and (for simplicity) let's assume the overall attendance happens to be the same at each event, say $A$ people (ranging between 1 ...
1
vote
0answers
25 views

Variance of exponential moving average

I'm not quite sure what the form for the rolling recursive variance should look like. I have that the recursive average is $m_t = \alpha x_t +(1-a)m_{t-1}$. Then would the rolling recursive variance ...
1
vote
0answers
32 views

Exponential smoothing and variance

I have a time series, let's denote it as $X_t$ (a series of prices). We exponentially smooth the data to obtain another time series, an exponential moving average: $EMA_t$. My question is how do I ...
3
votes
3answers
120 views

Average value of $e^{-x}$ from $0$ to $\infty$

I just signed up for this site so I hope I'm doing this right. I've been having trouble wrapping my head around the average value of the function $e^{-x}$ from 0 to $\infty$. I know that the average ...
0
votes
0answers
246 views

How to find the average velocity of blood?

The velocity $v$ of blood that flows in a blood vessel with radius $R$ and length $L$ at a distance $r$ from the central axis is $$v(r) = \frac{P}{4\eta L}(R^2 − r^2)$$ where $P$ is the pressure ...
1
vote
1answer
20 views

Average amplitude of the sum of N sines with random phase differences

We have N functions of the form $asin(kx+c)$ Their $a$ and $k$ values are the same their $c$ is a random number between $0$ and $2\pi$ $f(x)$ is the sum all N functions I know $f(x)=Asin(kx+c')$ ...
0
votes
2answers
29 views

Volume and Average Height

How do you calculate the average number of floors of buildings across a city block when all the buildings are varying heights. Followings in a listing of what the area looks like and the number of ...
0
votes
0answers
38 views

How can I calculate accuracy of an estimate based on a subset of data?

For example, say I'm trying to determine the average number of steps taken in a day for a population of 100M people. I know the exact number of steps for a random 25M subset of the 100M group (2500 ...
-1
votes
1answer
21 views

How can I get the average angle from a set of three points?

Please forgive me, but I'm not mathematically inclined and i'm trying to solve a problem for a video game i'm developing. My levels are composed of vector shapes and i want to find out what the ...
0
votes
0answers
11 views

Normalize and Average weighted

Everyday I receive a data of three variables (neutral, negative and positive). ...
0
votes
0answers
23 views

Boosting v. weighted average

I have been watching an MIT online Artificial Intelligence lecture by Prof. Winston about boosting. The boosting technique uses complicated maths to combine the results from several weak predictors to ...
14
votes
3answers
409 views

If my average speed is 50 mph, is it better to go 10% faster or 5 mph faster? (These are not the same)

BACKGROUND Suppose we have a journey between $A$ and $B$ where different sections of roads have different speed limits and our average speed is $50$ mph. If when I repeat the journey I travel $10\%$ ...
2
votes
0answers
43 views

What is the average maximum value of a set of random numbers? [duplicate]

Let $a_1, a_2, a_3, \ldots, a_{10}$ be ten randomly chosen real numbers in the interval [0,1]. Let $m$ be the maximal value out of these 10 numbers. What is the expected value of $m$? (i.e. If i ...
0
votes
0answers
27 views

Anyone have any good ideas on how to average 2D directions?

Directions, being a cyclical quantity (i.e. if you keep increasing the value, you'll eventually end up back where you started) can't be averaged out like regular numbers. For example, say I have 2 ...
0
votes
0answers
17 views

The average value of f on region R (double integrals)

If I am given f(x,y) and I calculate the average of the region given by the formula in this image should the average always = (min of f(x,y) +max of f(x,y))/2. I think this is only the case if the ...
0
votes
0answers
36 views

How can I calculate my current average for my class?

I'm trying to do some what-if scenarios for one of my courses and I'd like someone to double check my work. The grade breakdown is as follows: ...
0
votes
2answers
49 views

How do I calculate a combined data error?

I have a time series of data points read from an instrument, I also get an estimate of the error ($\sigma$) for each of these readings. e.g. $10.12 \pm 0.05$ $10.09 \pm 0.02$ $10.20 \pm 0.12$ ...
-1
votes
1answer
19 views

Buying forecast

I have a set of items. In 2013, I bought x of a certain item, in 2014 I bought y, and in 2015 I bought z. In many cases, I only bought the item in one year, like: ...