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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1
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4answers
13 views

Percentages not adding up

I have a series of percentages: 132/220 (60%) and 88/220 (40%). Now when I break them down into subcategories and then recalculate the percentages them come out 5% different. 81/140 (58%) and ...
0
votes
0answers
7 views

What is the confidence level of a curve fitted moving average forecasting next element in time series?

Suppose I got a time series X={X1,X2,X3,...,Xn}, and i got a Moving Average of any kind, it doesn't matter. The moving average is curve fitted to the timeseries of n elements, to fit exactly and most ...
-1
votes
1answer
16 views

Calculate the average grade Leslie must make in order to receive a B for the math class?

Leslie is taking a math class. This is how the class is graded. Test 1 13% Test 2 13% Test 3 13% Lab 1 10% Lab 2 10% Lab 3 10% Lab 4 10% Final Exam 21% She received a 93% on Lab 1, 70% ...
3
votes
1answer
78 views

How to find the function $f$ that satisfies $f(x, y) = f(x^{-1}, y^{-1})^{-1}$ and $f(x, y)$ is $\approx$ $average(x, y)$?

Fist of all, I'm a programmer, not a mathematician, and I'm sorry for my non native English. And I'm sorry if the question is not appropriate, it is my first time here. Or if the question has no ...
0
votes
0answers
4 views

Compute mean of a set from a biased sample

I want to compute the average of an unknown set $S$ containing real numbers. I can take arbitrary large number of samples from $S$, but the samples are not uniform, meaning that some numbers are ...
0
votes
1answer
25 views

calculus integration, average height of point on semi circle

i was recently watching a single variable calculus video of mit 18.01, lecture 23. in that it is said that average height of a point on semicircle with respect to arc length is 2/pi.I have a hard time ...
0
votes
3answers
31 views

How to compute Final Grade with assignment weightings?

I have just finished the Final for my Computer Hardware course, and I'm trying to figure out where my grade currently stands. The way the class is broken up is 50% weight for the homework, 25% for the ...
0
votes
2answers
29 views

Suppose the height $(m)$ of a ball is modeled by $s(t) = -4.9t^2 + 24.1t + 2$ where $0 \le t \le 5$ [closed]

Suppose the height $(m)$ of a ball is modeled by $s(t) = -4.9t^2 + 24.1t + 2$ where $0 \le t \le 5$ Find the time when the ball is 1m off the ground What is the function for average velocity from 1m ...
0
votes
0answers
40 views

About Bayesian formula and rating system

I'm building a scoring system with score from 0 to 5) and I would like to sort products according to the number of reviews and their scores. After some research on the Internet I have found two ...
0
votes
1answer
17 views

Getting the average of values with errors.

I have five data values each with an associated error. I want to find the mean of these values but also take the errors into account. How do I do this? Lets say the data values and errors are: ...
0
votes
0answers
15 views

How does an increase in the order count in a conditional mean model affect the model?

How does an increase in the order count in a conditional mean model affect the model ,especially the effect on its filtering capacity, smoothness, lag ; while also its forecasting ability. By ...
0
votes
1answer
19 views

Statistics question regarding mean of exponential distribution

So I have a question in front of me which reads: 'If component lifetime is exponentially distributed with parameter,obtain an expression for the proportion of components whose lifetime exceeds the ...
0
votes
0answers
15 views

Unweighted Mean of Percentages

I have come across an interesting problem, which I'm sure there must be a standard solution to, but lots of Googling hasn't yielded much (which may mean I'm well off track...). I am trying to ...
-2
votes
0answers
33 views

How do they calculate my grade average?

So in my online schoolwork they calculate my average for my final grade but I am unsure how they do it. Every week I have 1 discussion, and 1 assignment for 8 weeks. At the 4 week mark I have an exam ...
-2
votes
1answer
28 views

Problem related to averages. [closed]

The average height of the $10$ girls in class is $105$ cm. The average height of the $15$ boys in class is $125$ cm. What is the average height of all students in the class?
0
votes
2answers
19 views

Magnitude of Average Velocity

A train travels 100 miles toward 37 degrees northwest and then 90 miles north. The whole journey takes 2 hours. What is the magnitude of the average velocity of the train?
1
vote
3answers
55 views

Find the average test score for each of three groups, given overall averages

I've been working on this question for the last hour and cannot determine a solution. Q: 100 children, 200 teens and 300 adults write a test and an average is computed for all three groups. The ...
1
vote
2answers
34 views

Where should I use median instead of average?

Is there a general law, or rule of thumb, or rationale, when to use median and when average? Although I know the difference and how they are computed, when I try to translate to simple English I ...
0
votes
2answers
28 views

What exactly does the Geometric Mean actually mean ? When should I use it?

I am working signal demodulation and the RC value requires to be the geometric mean of the periods of the message signal and the carrier wave. I wonder why I need the geometric mean for this or why ...
0
votes
0answers
13 views

Average Cycle per Instruction

We have two different computers with the same instruction set. There are three classes of instructions (A, B, and C) in the instruction set. Computer M1 has a clock rate of 80 MHz and Computer M2 has ...
0
votes
1answer
35 views

Estimating how much two probability distributions differ

I have two probability distributions A and B. First I would like to estimate how much they differ. In this regard I use as metric the Jensen–Shannon distance (i.e. the square root of Jensen–Shannon ...
0
votes
1answer
15 views

In the loop average computation

I want to compute the average of a set of number, which is constantly increasing. I guess it's simple, but I'm struggling here: Let's say: 1st iteration: m(i)=a+b/2 2nd iteration: m(i+1)=a+b+c/3 ...
0
votes
1answer
16 views

Help with creating a formula to calculate grade needed on test to pass?

This is probably a simple math question and yet I'm struggling to understand it, any help would be extremely appreciated. Say if I have 2 test results, 50% on Test 1, test worth is 10% of final ...
0
votes
2answers
38 views

Using difference of average for identifying features in an image

I'm working with this paper: Textural Features Corresponding to Visual Perception, by Tamura, Mori, and Yamawaki. There's a part where you have to calculate neighborhoods of one image (matrix of, for ...
-1
votes
3answers
55 views

How to find the total amount from given percentage

I am trying to answer this question from internet for my mathematics practice. ...
-1
votes
1answer
33 views

How to solve averages without using formula

For the question, "The average of $30$ numbers is $40$ and that of other $40$ numbers is $30$. Find average of all numbers.", the options given are: $35$ $34$ $34\frac{1}{2}$ $34\frac{2}{7}$ I ...
0
votes
1answer
24 views

Finding the average of multiple ranges

I conducted a survey where participants inputted a range for their weekly tablet usage. For example, someone was able to say they used their tablet "11 - 15 hrs/week". How do I find the average ...
0
votes
1answer
12 views

Power of a square wave signal

I have a signal with half-amplitude $A$ and period $T$ and I want to calculate the average power of the signal. I think I remember the power of a signal $x(t)$ to be ...
2
votes
1answer
29 views

Average Number of Roots of a Polynomial modulo p

Let $f \in \mathbb{Z}[X]$ be an irreducible non-constant polynomial, and consider this polynomial modulo $p$ for each prime $p$. On average, how many roots does $f$ have modulo $p$? I.e., if $r(p)$ ...
37
votes
11answers
7k views

What is the average of no numbers?

I have two programs that both behave nearly identically: they both take in any numbers you give them and can tell you the average and how many numbers were given. However, when you don't give them any ...
2
votes
2answers
37 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
76 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
22 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
24 views

Calculating weighted score of test

I have a test containing questions with 3 levels of difficulty: ...
4
votes
1answer
561 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
31 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
31 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
27 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
47 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
46 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
77 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
32 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
28 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
38 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
55 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
22 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
35 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
52 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
139 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 ...