population Definition and 262 Threads

The National Center for Education Statistics monitors many aspects of elementary and secondary education nationwide. Their 1996 numbers are often used as a baseline to assess changes. In 1996, 31% of students reported that their mothers had graduated from college. In 2000, responses from 8368...

Suppose your polling methods were so good that all one had to worry about was random experimental error. Then how many sample subjects would you need to have 95% confidence that your sample mean was within 1% of the true population mean? Answer : Ten thousand sample subjects. That though...

Hello, 1) Let's consider a population of 1,000,000 data points with each data point being represented by the pair of values (x,y). Let's assume that, when plotted on a graph, the 1,000,000 points look like a spread out cloud with an overall positive linear trend. These 1,000,000 points...

ClearAll["Global`*"] (*R = reds, G = greys*) (*S = susceptible, I = infected, R = recovered*) tseries = {t, 0, 3}; vars = {HG[t], HR[t], SG[t], IG[t], RG[t], SR[t], IR[t], aG[t], qG[t]}; b = 0.4; (*natural mortality rate, both species*) \[Beta] = 0.7; (*rate of virus transmission*) aR =...

Hello! I have a 2 level system given by: \begin{pmatrix} 0 & A \\ A & Bcos(\omega t) \end{pmatrix} If I populate only one of the states initially, at ##t=0## the 2 states are B apart, while after half a period they are -B apart. Basically the system went from one side of the avoided crossing...

Please check the question below as given originally. Answer given is 25%. I am unable to proceed. It is given that the half-life is underestimated by 10% therefore it must be larger than originally estimated. What I can find using the percentage error formula is ##\left(...

Hello! I have two energy levels of opposite parity close by (we can assume they are far from all the other levels in the system) and an off-diagonal term in the 2x2 matrix Hamiltonian that weakly couples them. I initially populate only one parity state, say the positive one, and after a while...

I am refreshing on this... I think there is a mistake on the circled part in red...right? not correct symbol for sample mean...This is the part that i need clarity on. The other steps to solution are pretty easy to follow...as long as one knows the t-formula and also the knowledge to...

Hello. I've performed a Google search on the subject of Population III stars and come up with some results. But I'd now like to go a little further. Could I please be directed to articles and/or papers on this subject, so that I can further my interest? Thank you for any help given. Cerenkov.

Hello. I'm writing my Master Thesis about planetary population synthesis and one of the chapters is about the different models. I found that most of them are Bern models with some modifications. What is a Bern model in planetary population synthesis and what references can I read about it...

1. You are working in a company facing attrition problems of the customer service representatives for the past five years. The company president proposed that if the attrition rate is at least 10 per month, then the salary scale, compensation package, and professional development programs for...

1. Individual students’ scores on a national test have a normal distribution with a mean of 18.5 and a standard deviation of 7.8. At a Trade School, 84 students took the test. If the scores at this school have the same distribution as national scores, what is the mean, standard deviation and...

$\tiny{\textbf{6.8.7}}$ Kiaser HS Population Growth The population of a southern city follows the exponential law (a) If N is the population of the city and t is the time in years, express N as a function of t.$N(t)=N_0e^{kt}$ (b) If the population doubled in size over an 18-month period and...

The number of visible galaxies is to vanish in the long-term future with the ##\Lambda##CDM model (book and papers of L. Krauss et al). I am interested in a quantitative study on how the population of galaxies decreases; I could not find one so I do it myself: The scale factor...

As they are in engineering and manufacturing? I ask because during a very deep, post stroke marbles census in came to light that I had an extraordinarily high level of pattern recognition such that the department head said I was in the top .003 percent of the population. I ran the numbers...

https://www.worldobesity.org/news/statement-coronavirus-covid-19-obesity This is more of a medical practitioner's site than a research facility. This shows far greater impact on medical facilities and fatalities, apparently 90% of fatalities occur in chubby countries. News version...

I'm having trouble understanding stimulated emission and population inversion, and how they work together to make a laser work. I pretty much need this explained completely. 1. Spontaneous emission, they say, is when an atom absorbs and then later emits a photon. Isn't that just regular...

In a park , 200 foxes are tagged. In 100 sighting, 14 were tagged. Estimate the size of the fox population ? This is how approached . 200 tagged : Population 14 tagged : 100 (200x100/14)= Estimated Population = 1,429 I wonder if this is right !

My main reason for posting this is to prevent overreaction to the research, especially from the "pill press" internet people and the impact that has on non-science people. Yes, it is interesting. No, it is not definitive. Worried about it? Take a short 10 minute walk, 5 or 6 days a week, in...

Germany has been virus testing in groups of 10. In a high risk population where p=1/100 this requires, on average, 196 tests to test 1000 people. In a moderate risk population, it requires 109 tests to test 1000 people. But if they were to test in groups of 32 in such a population one would...

https://www.npr.org/sections/thesalt/2019/09/25/764243209/prehistoric-babies-drank-animal-milk-from-a-bottle Neolithic animal shaped baby bottles were shown to have non-human milk residue. One reasonably likely outcome is that women who stopped nursing early and used the "bottles" to feed...

image to avoid typos Ok I'm clueless,

I've only recently started my journey into physics. While on this journey I realized quite a bit of the dumb down scientific information given to the public may not have been completely accurate or presented in a way that resulted in an inaccurate understanding. Lately I've been spending most of...

I know that standard deviation of whatever data is defined as sqaure root of square difference from mean value: ##\sigma(data)=\frac{\sum_{x \in data}((x-x_{mean\ of\ data})^2)}{|data|}=\frac{\sum_{x \in data}((x-\sum_{y \in data}(y)/|data|)^2)}{|data|}## but sometimes formula...

Monthly Cycle numbers Here is the cycle ratio: $$2_{early}:2_{fertile}:1_{late}$$ And the numbers: $$20,000_{early}:20,000_{fertile}:10,000_{late}$$ Now, let's divide the early into 2 groups, pre-fertile, and safe and assume there is a 50/50 split between those 2 groups. Let's also assume...

I want to estimate the number of male and female cattle produced over a period of time (say, five years and ten years) from an initial stock of 30 heifers, all 18 months of age at which age they are first joined (mated). Assume that the first calf is born when the mother is 27 months old...

Let X1, · · · , Xn be a simple random sample from some finite population of values {x1, · · · xN }. Is the estimate $$\frac{1}{n} \sum_{i}^{n} f(Xi)$$ always unbiased for $$\frac{1}{N} \sum_{i}^{N} f(xi)$$ no matter what f is?My thinking: I don't think all f's are unbiased, because not all...

In modern stars, the more massive a star is, the more likely that it is powered by the CNO fusion cycle, where Carbon, Nitrogen, an Oxygen act as catalysts for creating helium from hydrogen. In stars over 1.3 solar masses, this is the primary fusion process. Below that that level it's a mix of...

Popular science version: (Let me know if the link has problems) https://www.washingtonpost.com/science/2018/10/15/hyperalarming-study-shows-massive-insect-loss/?utm_term=.f9b8006df72b Long term sampling from the 1970's to 2017/2018 shows losses of insect, arthropod, and insectivore populations...

The population of a bacteria culture doubles every 2 minutes. Approximately how many minutes will it take for the population to grow from 1,000 to 500,000 bacteria? Can someone set up the proper equation needed? I can then work it out.

Hey, I found an interesting algebra problem combined with log. It was quite an unique one so I wanted to share it with you guys. Problem: There is a city where the population increases at a constant rate. At the end of 2016, the population of the city was 2 times larger than the population...

I need my formula checked. It involves pregnancy rate, miscarriage rate, stillbirth rate, time breastfeeding, average generation length, multiples, and average number of pregnancies. So let's start off with the conditions: Plenty of food and water for millions Cosmic ray protection...

1. Homework Statement You’re testing the effect of a noxious substance on bacteria. Every 10 minutes, one-tenth of the bacteria which are still alive are killed. If the population of bacteria starts with 10^6, within which period of 10 minutes will 70% of the bacteria be killed? Homework...

The next questions will be in english and spanish, since my birth language is spanish I may be mistaken in a few english words. --------------------------------------------------------------------------------------------------------------------------------------------- Spanish Debo advertir que...

Hi I am going through Edx course on Introduction to Differential Equations by Paul Blanchard (BUx: Math226.1x). At one point, he is explaining the Logistic population model.$$\frac{dp}{dt} = kp\left(1- \frac{p}{N}\right) $$ After this, he says that since the right hand side does not involve t...

If I have a starting population of 200 people with an average life expectancy of 35 and a yearly growth rate of .10, what will my population be in 1,000 years?

Homework Statement with an individual lines at its various windows , a post office finds that the standard deviation for normally distributed waiting times for customers on Friday afternoon is 7.2 minutes . The post office expreiemets with a single, main waiting line and finds that for a random...

Homework Statement A city surrounds a bay as shown in Figure 1. The population density of the city (in thousands of people per square km) is f(r, θ), where r and θ are polar coordinates and distances are in km. (a) Set up an iterated integral in polar coordinates to find the total population...

6d Anotherdisease hit the the chronically ill town of College Station, Texas. This time the percent of the population infected by the disease $t$ days after it hits town is approximateled by $$p(t)=10e^{-t/8},0 \le t \le 40$$ a. After how many days is the percent of the population infected a...

...from suffering inbreeding and decline into a non-viable number of animals? Assume a creature somewhat larger than the average human. And with bigger feet. Mods, if this needs moved go for it.

Homework Statement The Pacific halibut fishery has been modeled by the differential equation. \displaystyle\dfrac{dy}{dt}=ky\left(1-\dfrac{y}{M} \right) where y(t) is the biomass (the total mass of the members of the population) in kilograms at time t (measured in years), the carrying...

Base isolated population is 1000 females. Each is one is on average 25 and lives to be 100 years old and gives birth to three kids...sperm banks so there are no men in the first generation population. 2nd generation is 50%male and 50% female and each female grows up and has three kids. Everyone...

Homework Statement [/B] A new concrete mix is being designed to provide adequate compressive strength for concrete blocks. The specification for a particular application calls for the blocks to have a mean compressive strength μ greater than 1350 kPa. A sample of 100 blocks is produced and...

Homework Statement Hey guys I'm struggling to find much information of modelling single species population dynamics that relates to this question. A question like this is going to be coming up in my final exam and I need to be able to solve it. I'm struggling to even know where to start. I'm...

I recently read this article. It discusses how we can use statistical methods to provide estimates of species population given little information about the actual population and other factors that make up the ecosystem. This is all fine, and i understand the importance of obtaining information...

I was just wondering: why does lower kinetic temperature imply population inversion? I've read this is true in a few (astrophysics) texts regarding molecular clouds, although this seems to be a more general result that I haven't really read an entire explanation for. Nevertheless, do you have...

Homework Statement Joan’s finishing time for the Bolder Boulder 10K race was 1.75 standard deviations faster than the women’s average for her age group. There were 405 women who ran in her age group. Assuming a normal distribution, how many women ran faster than Joan. Homework Equations The...

You are interested in studying the relationship between sodium consumption and the development of hypertension. 32% of Americans are hypertensive (systolic blood pressure>140), and a further 29% are prehypertensive (140≥SBP>120). Detecting a 1 mm Hg SBP elevation with 80% power at the 0.05%...

Couldn't figure a better thread title but my question is as follows. Intro... I was bought up to think that any suggestion to limit population growth from a state level is like the most evil suggestion. Given that science will prolly always find ways to feed people I would like to leave food...