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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2answers
39 views

Average Growth Rate for Year 1 across 5 groups

Lets suppose that I am measuring the total number of online visitors to 5 websites on a monthly basis. I have this data for the months of Jan - Dec. What I want to understand is "What is average ...
1
vote
2answers
93 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 ...
0
votes
0answers
24 views

The use of Weighted arithmetic mean to determine the extent to which the data correspond

I don't know when I can ask such question, because it is not a completely mathematic question. I have a text and a topic (single word). I want to check how much this text corresponds to the topic. ...
0
votes
1answer
26 views

Calculating weighted score of test

I have a test containing questions with 3 levels of difficulty: ...
4
votes
1answer
568 views

Sum of averages to averages of sum

I have the following values $\overline{b}$, and $\overline{u}$ which is : $\overline{b} = \dfrac{b_1+b_2+b_3+b_4}{7}$, $\overline{u} = \dfrac{u_1+u_2+u_3+u_4}{7}$ is there any way I can get the ...
1
vote
2answers
33 views

For any base-$n$ number system, what is the average length of a number $\leq100$?

By this I mean the amount of symbols (bits / digits / etc. ) for any number from $0$ to $100$. I don't know whether this can be answered, I'm just asking out of interest - not homework or anything.
0
votes
0answers
34 views

find the no. of wagons need to be attached

The speed of an engine is proportional to the square root of the number of wagons attached to it. Without any wagons attached to it the speed of the engine is 60km/hr. With 16 wagons attached to it ...
0
votes
0answers
29 views

Problem of EOQ under conditions of uncertainty

I have solved the following problem for one half. Please help me to solve it full. A restaurant offers, at noon, only one menu at a fixed price of Euro 15. The cost of each meal is 12 Euros. From the ...
0
votes
1answer
58 views

Find average stream velocity over a cross-section of a cylinder, given $v(r) = k(R^2 − r^2)$

I'm doing integration homework and a question that I am not sure how to approach popped up. The velocity (in centimeters per second) of blood r cm from the central axis of an artery is given by ...
0
votes
1answer
47 views

Calculating average over a year

I'm trying to calculate the average count of employees for a group of companies. I need to exclude months where a a company had no employees. Please verify that my approach is correct. ...
0
votes
0answers
100 views

Average and Standard Deviation for Angular Values

I'm trying to characterize an inexpensive accelerometer that provides (roll, pitch, yaw) values by generating basic running statistics (mean and standard deviation). But I'm unfamiliar with ...
0
votes
1answer
34 views

How do I “recalculate” a median number?

I'm not sure how to explain the question, so I'll do it by an example. The median age in some country is 41.7. 50% is younger than 41.7, 50% is older. How would I calculate the percentage of the ...
2
votes
0answers
56 views

Compute average and maximum value of a field over a streamline

I'm working on a code solving a set of PDEs. I have a vector field, $\vec{v}(x,\theta,z,t)$ (it's a velocity) and a scalar field, $c(x,\theta,z,t)$. I have a $2\pi$-periodicity in $\theta$. The ...
0
votes
1answer
29 views

Probability static area is greater than variable area

I have a rectangular section of constant height and length and I choose a random starting point anywhere along its length. From the randomly chose starting point, I first add ...
0
votes
0answers
39 views

What is this called specifically?

Imagine you take a radius from the center of the shape, you add up all of the lines as it rotates 360 degrees. The radius is measured from its point of rotation, like (0,0) in Cartesian coordinates,to ...
3
votes
3answers
56 views

The average value of the function $y=\tan(2x)$ over the interval $[0,\frac{\pi}{8}]$

I was given the following question in a technology free exam. How would one go about solving this without the use of a calculator? NB. I am currently in my last year of high school so please don't ...
0
votes
1answer
25 views

Average value for multiple integrals

If there is a function $f(x,y)$ and we want to find the average value over a region $R$ defined by $0<x<1$ and $0<y<x$, how is that computed? I know that it would be something like this: ...
1
vote
1answer
38 views

Sum and sum of average not matching

I'm struggling with the following problem. I have a table showing the % of a population that like (say) bananas in three locations, the population of each location, and the total population who like ...
2
votes
1answer
59 views

Does “Expected Absolute Deviation” or “Expected Absolute Deviation Range” exist in stats and have another name?

So everyone is familiar with Variance and Standard Deviation from high school, but it seems no one has any familiarity with a philosophical justification for such weird, seemingly arbitrary measures. ...
0
votes
2answers
262 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 ...
2
votes
1answer
171 views

Time to extinction

Suppose that a population has a rate of extinction equal to $k \exp({-\epsilon N})$ where $\epsilon$ and $k$ are constant and $N$ is the population size. This also means that the time to extinction is ...
0
votes
1answer
39 views

Help with finding the arithmetic mean of all the radii from the center to the edge of an ellipse?

So far I approached this problem computationally, I decided to take all the radii add them up, by distance formula, then divide by the number of radaii. To make the distribution even, I rotated the ...
0
votes
0answers
34 views

Problem calculating the average power of a vector?

I am calculating the average power of a vector. I would like to compare the final expression with the simulation. However, they are not equal. Please help me to point out which steps are wrong. Thank ...
0
votes
2answers
57 views

Computing the average difference in a list of numbers

I have a list of numbers 280, 449, 689, 959, 1360, 1740, 1139 so there is between 289 and 449 is a distance of 169 and then between 449 and 689 a distance ...
0
votes
1answer
21 views

Features of a Set Given Same Value for Maximum and Average

What else, if anything, can be said if the maximum of a set is equal to the average value in the set? If the average is equal to both the maximum and minimum then all the values are the same, but can ...
0
votes
0answers
26 views

Economics Marginal Cost and Average Cost

I am in Computer Engineering but this year the university gave me choice for two electives with one being Psychology and the other Economics...So this being my first economics course I am really ...
0
votes
1answer
39 views

How to normalize a slope?

Say I have two slopes and two averages for a sample: $m=4{,}000$ dollars/day, average $a=50{,}000$ $n=80{,}000$ dollars/day, average $b=700{,}000$ Graphically, $n$ is very ‘steep’ compared to $m$. ...
3
votes
1answer
40 views

Is the norm of the average $\le$ the norm of the max?

Given $\pmb X \in \mathcal{R}^p$, denote the elements of $\pmb X$ as $\pmb x_i$ for $i= 1, \dots, n$. Denote the $t(\pmb X)$ as the average of $\pmb X$ \begin{equation} \pmb t(\pmb X) = \frac 1 n ...
1
vote
1answer
25 views

fast solve average

there are Indians and Europeans in an army of 12,000. the average height of Europeans is5'10" and that of Indians is 5'9" and the average height of entire army is 5'9,3/4. find out the number of ...
1
vote
3answers
44 views

Covariance Issue with a joint distribution

Here is the problem: Let $X$ and $Y$ be continuous random variables with joint density function: $$f(x,y) = \frac{8}{3}xy\text{ for }0 \le x \le 1\text{ and }x \le y \le 2x $$ I'm trying to find ...
1
vote
2answers
101 views

How to establish this inequality: $(1-a)(1-b)(1-c) \geq 8abc$ for $a+b+c=1$?

Let $a$, $b$, and $c$ be positive real numbers such that $a+b+c = 1$. Then how to establish the following inequality? $$ (1-a)(1-b)(1-c) \geq 8abc.$$ My effort: Since $a+b+c =1$, we can write $$ ...
3
votes
1answer
47 views

What is the most elementary proof of these inequalities?

Let $p$ be a non-zero integer, and let $x_1$, $\ldots$, $x_n$ be $n$ positive real numbers. Then we define the $p$-th power mean $M_p$ of these numbers as $$ M_p \colon= (\frac{x_1^p + \ldots + ...
1
vote
2answers
32 views

Proving that mean KDR in a videogame is one

This is not related to schoolwork. A friend of mine challenged me to prove that the mean KDR (assuming players can only die at the hands of other players) must always be equal to one. I have gotten ...
0
votes
1answer
52 views

How to find the average value of a discontinuous function

A car covers $\frac{1}{3}$ distance with speed $20\frac{m}{s}$ and $\frac{2}{3}$ with $60\frac{m}{s}$. What is the average speed over the entire interval? Due to the discontinuity of the function, I ...
0
votes
2answers
29 views

Comparing / Averaging two very different numbers

I have two examples called a and b. Each example has two scores: a: 0.5 and 0.001 b: 0.8 and 0.0001 If the higher score wins, then b wins when looking at the first set (0.8 > 0.5). But I also want ...
0
votes
1answer
30 views

What ratio of students in a 20-student class with total average of 17.06 got at least 17?

The maximum score is at most 20. The class has 20 students. For math exam the average of the whole class is 17.06. How many per cents of the class got at least 17 out of 20 in the exam?
0
votes
1answer
25 views

Average sum of seria

I need some help with the next question in probability: In the range {1,2,...,100}, someone picks randomly 15 different numbers, with the same probability for each number. What is the average sum ...
0
votes
1answer
22 views

How should I calculate weighted average in this case?

If there is a product, whose price depends on its quality, and these price values are: [0.6; 1.1; 1.3; 2.0; 4.2; 21.6] Lets assume that there is some kind of a lottery, and I can by a ticket for it ...
1
vote
1answer
15 views

Working out a parent percentage from child percentage

I am currently working on a performance indicator system for the number of reviews due on a bunch of document against the number that were due in that month as a percentage. There are several areas ...
0
votes
2answers
41 views

average and total average

why is it when I get the average of the column "per hour", it's different from the total?
18
votes
8answers
3k views

Unorthodox way of getting the average of two numbers

I can't believe the alternative method I just saw to calculate the average of two numbers: ...
0
votes
3answers
43 views

Help with question about Normal distribution

The heights of people at some city is $N(\mu,\sigma^2)$. 25% of the people are above 176 cm. and 20% are below 165 cm. How do I found $\mu,\sigma^2$? We choose randomly a group of 100 people. What ...
0
votes
0answers
37 views

Mean values using eigenvalues - how?

I thought the definition of the average value of $f(x)$ was $f* = \frac{1}{T}\int_0^T f(t)dt$ How do I get from this definition to the definition of the mean value of a function in terms of ...
0
votes
1answer
25 views

Approximate simple moving average knowing only previous SMA?

I know it's possible to calculate a regular average incrementally knowing the previous average, the next number and the number of items. But is this possible for a moving average of N items, at least ...
0
votes
2answers
201 views

Calculating average value of points over a period of time

I have several values plotted over a period of time on a line graph. The length of time between values is not uniform (i.e. one value could be 3 days after the one before, which itself could be 2 ...
0
votes
1answer
37 views

Average value calculation

A company has 2 mines: A and B. The production per person in mine A was 22,6 tons last year, and 27,9 tons in mine B. Last year 60% of the total production came from mine A. The question is the total ...
2
votes
1answer
26 views

Problem about average of cos square (nt) where n is arbitrary

I often see people just say time average of cos^2(nwt) is 1/2, I want to know in what cases this is not valid? w is just the frequency, can be assumed as a constant. Assuming you are always ...
0
votes
1answer
31 views

Mean squared [X] or Mean [X] squared?

If I have two functions, as below, which one is "Mean [X] squared" and which is "Mean squared [X]"? Would I be correct in saying the former is number 1 and the latter is number 2? Thanks in advance ...
2
votes
1answer
16 views

Choosing two sets of values with the least difference between the averages of the sets

This is probably a simple Combination problem but I can't think of how to solve it in LibreOffice. I run multiplayer games along with seven of my friends, on two teams of 4 players each, for a total ...
1
vote
1answer
37 views

Does missing a number from a set affect the average?

Firstly, apologies for an uninteresting title, and whether this is absolutely newbie maths. I'm a programmer, and when it comes to maths and me - the wheel is going, but the hamster is dead. On To ...