population Definition and 278 Threads

Population is the term typically used to refer to the number of people in a single area. Governments conduct a census to quantify the size of a resident population within a given jurisdiction. The term is also applied to animals, microorganisms, and plants, and has specific uses within such fields as ecology and genetics.

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  1. A

    Chi Squared and Gaussian Population Question

    The following data represent a frequency distribution of 200 variables drawn from a parent Gaussian population with mean=26.00 and standard deviation=5.00. the bins are 2 units wide and the lower edge of the first bin is at x=14. 4;8;11;20;26;31;29;22;26;13;5;2;3 a. plot a histogram of these...
  2. C

    ODE Population Problem: Proportional Growth with Time and Monthly Increase of 20

    I know that the rate of change with time of a population is proportional to the square root of t. T=0 is y = 100. Population increases at rate of 20 per month. I started out by trying to do dy/dt = p^.5. I am used to the population problems where I use y=Ce^(rt) but am having trouble...
  3. K

    Maximum Sustainable Earth Population

    Climate change and environmentalism are some of my favourite areas of science and from both reading around and going to lectures I've got two figures for the maximum sustainable population of the earth, those being: 1 billion - from James Lovelock (one of his Gaia books) 1-2 billion - from...
  4. C

    I think human population is too much.

    Hello, Chitose here this is first time I post 'talk' instead of 'question' ....... well, you know that world weather these day is gone haywire. so... most of people know what the cause (Global worming, El Niño, bla bla bla) but what the main root of all this problem? Here's what...
  5. B

    How Does Population Affect the Value of Land and Currency?

    I also could have titled this thread "Argument for Fixed Money Supply". First of all the term 'value' will be defined as: "relative worth, merit, or importance". Also fixed: "not subject to change" This argument is based on two truths...
  6. B

    Differential Equations and population

    Homework Statement Consider a population p of field mice that grows at a rate proportional to the current population, so that dp/dt=rp. Find the rate constant r if the population doubles in 30 days. Find r if the population doubles in N days. Homework Equations ...The Attempt at a Solution...
  7. B

    How Does Genetic Linkage Affect Effective Population Size?

    Hi guys, Got a semester exam on Population Genetics coming up in a few weeks and I'm really struggling to get my head around this concept. I've read a number of internet sources but am still not completely certain of what it is. Could anyone give me a basic overview, also I've got it...
  8. T

    Consider a random sample n from a population

    Problem: Consider a random sample n from a population with probability distribution f(x,p) that depends on parameter p. Find the maximum likelihood estimator for p when f(x,p) = p^x (1-p)^1-x for x=0,1
  9. A

    Help with population of various isotopes in decay chains (Bateman equations)

    (Apologies for cross-posting this in the Nuclear and Differential Equations forums. I'm new to posting on Physics Forums and not entirely sure where it belongs. Mods, please feel free to delete/move as appropriate.) I am trying to create a decay chain simulator in Excel that my pupils can use...
  10. A

    Help with population of various isotopes in decay chains (Bateman equations)

    (Apologies for cross-posting this in the Nuclear and Differential Equations forums. I'm new to posting on Physics Forums and not entirely sure where it belongs. Mods, please feel free to delete/move as appropriate.) I am trying to create a decay chain simulator in Excel that my pupils can use...
  11. B

    Does Population Affect Gravity?

    Ok in my physics class we are doing planetary motion and stuff, we started talking about how the population of the Earth affects the force of gravity. So my question is does it? Also if say all of Earth's population was concentrated to one hemisphere and everyone jumped at the same time would it...
  12. X

    Calculating Aphid Population Growth: A Summer Homework Problem

    Homework Statement In summer months, female aphids reproduce by parthenogenesis, giving birth to females from unfertilized eggs. These females mature within 24 h and begin reproducing in the same way. Assume that each female aphid produces two females the day after she herself is born, then...
  13. L

    Expected variance of subset of population

    I want to calculate expected variance of a randomly selected subset of a population. The particular problem I am trying to solve is as follows. There is a set of values X = {x1, ... , xn}. Let Y be subset of X with n-1 elements. I think that if Y is selected at random (that is, if is...
  14. S

    Probability of a Population greater than the one of a sample

    I'm working on my statistics homework. The professor gave us two problems with the same probability (p), but with different number of trials (n); p= .3 and n= 2 in one and n= 200 in the other one. He told us one was the actual population and the other one was a sample. I did both problems and...
  15. S

    Comparing Sample Mean and Population Mean

    I thought that they were both the same, they're mean of the sample aren't they?
  16. H

    Population Equilibrium Solutions Differential Equations

    Homework Statement Consider the following model for the populations of rabbits and wolves (where R is the population of rabbits and W is the population of wolves). dR/dt = .05R(1-.00025R)-.00109375RW dW/dt = -.04W+8e-05RW Find all the equilibrium solutions: In the absence of...
  17. J

    Koala Bear Population Limits and Growth: A Mathematical Analysis

    Homework Statement The population of koala bears within a nature reserve at time t is greater than or equal to 0 is given by the function N(t) = 200t/4 + t Determine a)the lim as t-->infinity (the limiting population size) b)when the population is...
  18. V

    Need help on setting up an equation of population

    1. So for my computer science course I was given the homework on how to write a program on population growth. The serious dilemma is how to set up the equation. Here are the variables that are given to me: J = original number of Jackalopes (the imaginary animal that my teacher used) Y =...
  19. S

    Population Growth with Finite Resources:

    Homework Statement Homework Equations <see above>The Attempt at a Solution I'm a bit unsure how to set this up to solve for a solution. Any advice? Its obviously a separable differential equation. But I'm unsure what it is I'm looking for. This looks different then some population...
  20. S

    Systems and Signals Models - population model

    Homework Statement At the beginning of the year 2000, country A had a population p of 100 million people. The birth rate is 4%/year and the death rate is 2%/year, compounded daily. Every day, 275 immigrants enter country A. Neglect leap-year effects. Write a difference equation for the...
  21. M

    Calculating and Plotting ln World Population: 1900-1980

    For the period from 1900 to 1980, calculate the log base e (ln) of the world population values and plot these values on the vertical axis against the year on the horiontal axis. Draw the best straight line you can through these points and determine its slope, k. What is the exponential...
  22. H

    How Can I Sample a Smaller Population with a Given Beta Distribution?

    i have a population of items and i calculate how similar each item is to the rest of the items in the population. i store these values in a symmetric nxn similarity matrix. when i look at the distribution of scores, they follow a beta distribution -- most similarity scores are close to 0 (the...
  23. L

    Isolated Human Population: A New Species?

    If there was an isolated human population that eventually became unable to breed with any humans outside of their population, would they become classified as a different species than us?
  24. P

    Cross correlation in two data sets of the same sample population

    I have the following problem: Suppose there is a survey of persons with two properties each (a and b). a can take a relatively small number of values (say the political inclination: Conservative, Liberal, Socialist, or Other) the other one b can take a large number of values (say: the country...
  25. T

    Differential equations help, modelling population

    in a scientific study, the size , p of a population at t hours is being studied. Initially p = 560 and after 6 hours, p is found to be 1218. In a simple model of population growth, the rate of the population is taken to be proportional to the population at that time. Using this model predict...
  26. C

    How Many People Can Earth Sustain?

    Recently watched a documentry(BBC Horizon - How Many People Can Live on Planet Earth 2009) and its scary, could be worse than Global warming.. There are almost 7 billion people in the world today and numbers are increasing rapidly. Soon there'll be 8-9 billion people and we'll all feel the...
  27. M

    World Population Growth: When Will 11 Billion Be Reached?

    Homework Statement The population of the world was 5.7 billion people in 1995 and 6.2 billion in 2008. Assuming exponential growth by what year will the population reach 11 billion? The Attempt at a Solution i started by trying to find R but am not sure the my way is right...
  28. S

    When will the fish population be reduced to 10,000?

    Homework Statement The fish population in a lake is attacked by a disease at time t=0 with the result that the size P(t) of the population at time t: dP/dt= -k*sqrt(P) where k is a positive constant. If there were initially 90,000 fish in the lake and 40,000 were left after 6 weeks, when...
  29. C

    What is the Solution to a Population Growth Differential Equation?

    Homework Statement Consider a population whose number we denote by P . Suppose that b is the average number of births per capita per year andd is the average number of deaths per capita per year. Then the rate of change of the population is given by the following differential equation...
  30. A

    What Is the Standard Deviation of the Sample Mean for an Infinite Population?

    Homework Statement Consider an infinite population with the mean of 160 and a standard deviation of 25. A random size 64 is taken from this population. What does the standard deviation of the sample mean equal to? Homework Equations How do I answer this question without a given...
  31. P

    What is Coherent Population Trapping in Optics?

    Could anyone explain me (or give reference to a book) what is coherent population trapping (in optics). Is it somehow connected with Electromagnetically Induced Transparency (I also don't know how it works). Thanks for any replies.
  32. S

    Any hope for this PDE? Diffusion in population genetics

    I'm working on a problem in multi-allele diffusion in population genetics and I have come to this PDE: 0 = (tp_1(1-p_1)-sp_2)\frac{\partial u}{\partial p_1}+(sp_2(1-p_2)-tp_1)\frac{\partial u}{\partial p_2} + \frac{p_1(1-p_1)}{2}\frac{\partial^2 u}{\partial p_1^2} +...
  33. S

    Population curve and calculations

    Suppose rabbit populations grow exponentially with a growth rate of 20% per year. If P(t) is the population at any time t and 1000 is the initial (t=0) population of rabbits, what is the population of rabbits in 10 years? Use the DE model: P ' = kP with k = .1 and P(0) = 1000. Plz help me
  34. F

    When will the alligator population in the swamp reach four dozen?

    Working on some DE homework and need a tad bit of guidance. I got fairly far, I'm just wondering what the next step is. Homework Statement The rate of change of an alligator population P is proportional to the square of P. The swamp contained a dozen alligators in 1988, two dozen in 1998...
  35. S

    Differential Equation population question.

    Hi could someone please explain how this can be done please 1. The population P satisfies the differential equation dP dt = X(P) − Y(P) , where X(P) is the birth rate and Y(P) is the death rate. Find the general solution P(t) to this differential equation for the case that X(P) = k1(sqrt)P...
  36. S

    Solving Population Decline: Differential Equation with Birth and Death Rates

    Hi could someone please explain how this can be done please 1. The population P satisfies the differential equation dP dt = X(P) − Y(P) , where X(P) is the birth rate and Y(P) is the death rate. Find the general solution P(t) to this differential equation for the case that X(P) =...
  37. T

    Population growth using logarithims

    Homework Statement A culture begins with 100,000 bacteria and grows to 125,000 bacteria after 20 min. What is the doubling period to the nearest minute? Homework Equations Current=Original(rate)^time The Attempt at a Solution I can get make the first part out...
  38. M

    Differentials: Population moving model

    Homework Statement The population of a country is divided in two groups: People who live in rural areas (R(t)) and people who live in urban areas (U(t)). People move from rural to urban areas with a rate m and from urban to rural areas with rate n. a) Introduce the fraction of...
  39. R

    Character Displacement & Population Dynamics of Galapagos Finches

    Population Dynamics! Homework Statement 2 species of ground finch, Geospiza fuliginoas and Geospiza fortis, living in the Galapagos Islands display interesting variations in bill size. On the island of Santa Maria, inhabited by both species, the average bill depth of the G.fuliginosa is 8.1...
  40. G

    Estimating Population Variance from Observations

    Suppose the population variance \theta is to be estimated from observations Y_1, Y_2, \dots, Y_n using \hat{\theta} = \left(\frac 1 n \sum_{i=1}^n (Y_i - \overline Y)^2\right) where \bar{Y} is the mean. when it didnt say which distribution Y_is are? thanks
  41. X

    Predicting Population Growth in 1900 with Stewart 275/05

    I have this delete s275x05.txt; diary s275x05.txt clear; clc; close all; echo on % % Stewart 275/05 % year=[0:1]; % n+1 = year + 50 pop=[728 906]; p=polyfit(year,log(pop),2) plot(year,pop,'o','MarkerFaceColor','r') hold on x=[0:0.01:6]; y=exp(polyval(p,x)); plot(x,y) hold on %part...
  42. S

    What is the Growth Rate Constant for Population Growth?

    Homework Statement http://img14.imageshack.us/img14/1286/99892583.jpg Homework Equations in the pictureThe Attempt at a Solution so i know that p(0)e^2k = 950 p(0)e^8k = 9500 how do i find k? for p(0) i get 440.950939 is that right? btw. ignore the answers in the picture
  43. B

    Derivative Word Problem - US Population

    Homework Statement (a) Use a graphing calculator or computer to fit an exponential function to the data. Graph the data points and the exponential model. How good is the fit? (b) Estimate the rates of population growth in 1800 and 1850 by averaging slopes of secant lines. (c) Use the...
  44. Y

    Probability (Normal population distribution)

    Can anyone help me to solve this question: A random sample of twenty-five apples is obtained from a normal population distribution with a mean of 80 grams and a standard deviation of 5 grams. Another random sample of 36 apples is obtained from a population distribution having a mean of 75...
  45. K

    Population Model: Increasing P as t Increases

    Homework Statement The differential equation \frac{dP}{dt} = P(a - bP) is a well-known population model. Suppose the DE is changed to: \frac{dP}{dt} = P(aP - b) Where a and b are positive constants. Discuss what happens to the population P as time t increases. Homework Equations...
  46. N

    Which Rejection Region is Most Appropriate for Tennis Racket String Preference?

    Each of a group of 20 tennis players is given 2 rackets, 1 having nylon strings and the having gut strings. After several weeks of playing with 2 rackets, each player will be asked to state a preference for one of 2 types of strings. Let p denote the proportion of all such players who prefer...
  47. Spinnor

    Human population verses time, fourier transform of that function .

    Human population verses time, Fourier transform of that "function". Let the human population of the Earth be plotted verses time. Assume that this function is almost continuous. What would a Fourier Time Transform of that function look like? Is there a "strong" exponential component of...
  48. K

    How to estimate the future global population

    Hello everybody! I have been reading about the evolution of population growth since 1950 till now. It had many factors such as development of technology, of medecine, ... Now i want to calculate the future population growth let's say for example for 2050. In those readings i found also those...
  49. K

    How to estimate the future global population

    Hello everybody! I have been reading about the evolution of population growth since 1950 till now. It had many factors such as development of technology, of medecine, ... Now i want to calculate the future population growth let's say for example for 2050. In those readings i found also those...
  50. C

    Calculating radiation risk for a given population

    Hi This is the question... The population of the Marshall Islands were exposed to fallout from atomic bomb tests in the middle of the last century. A significant quantity of the fallout was in the form of 131Iodine, a gamma emitter which is avidly absorbed by the human thyroid. The average...
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