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相关概念视频

Population Growth00:57

Population Growth

Population size is dynamic, increasing with birth rates and immigration, and decreasing with death rates and emigration. In ideal conditions with unlimited resources, populations can increase exponentially, which plots as a J-shaped growth rate curve of population size against time. This type of curve is characteristic of newly-introduced invasive species, or populations that have suffered catastrophic declines and are rebounding.However, realistic environmental conditions limit the number of...
Cross-Sectional Research01:50

Cross-Sectional Research

In cross-sectional research, a researcher compares multiple segments of the population at the same time. If they were interested in people's dietary habits, the researcher might directly compare different groups of people by age. Instead of following a group of people for 20 years to see how their dietary habits changed from decade to decade, the researcher would study a group of 20-year-old individuals and compare them to a group of 30-year-old individuals and a group of 40-year-old...
Conservation of Declining Populations02:07

Conservation of Declining Populations

Conservation of declining population focuses on ways of detecting, diagnosing, and halting a population decline. The approach uses methods to prevent populations from going extinct.
Convenience Sampling Method00:55

Convenience Sampling Method

Sampling is a technique to select a portion (or subset) of the larger population and study that portion (the sample) to gain information about the population. Data are the result of sampling from a population. The sampling method ensures that samples are drawn without bias and accurately represent the population.
Convenience sampling is a non-random method of sample selection; this method selects individuals that are easily accessible and may result in biased data. For example, a marketing...
Sample Proportion and Population Proportion01:20

Sample Proportion and Population Proportion

Collecting samples or responses from an entire population takes significant time and effort, so a researcher collects responses from only a sample of that population. Suppose a study needs to collect information about a specific mobile application. After sample collection, the researcher analyzes the data and discovers that most individuals in the sample use that specific mobile application. The sample proportion measures the number of individuals in a sample who either use or don't use the...
Testing a Claim about Population Proportion01:24

Testing a Claim about Population Proportion

A complete procedure for testing a claim about a population proportion is provided here.
There are two methods of testing a claim about a population proportion: (1) Using the sample proportion from the data where a binomial distribution is approximated to the normal distribution and (2) Using the binomial probabilities calculated from the data.
The first method uses normal distribution as an approximation to the binomial distribution. The requirements are as follows: sample size is large...

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相关实验视频

Updated: Jul 5, 2026

Methods of Soil Resampling to Monitor Changes in the Chemical Concentrations of Forest Soils
09:16

Methods of Soil Resampling to Monitor Changes in the Chemical Concentrations of Forest Soils

Published on: November 25, 2016

重新填补农村:1980年人口普查的一个趋势

L Long, D Deare

    Science (New York, N.Y.)
    |September 17, 1982
    PubMed
    概括

    人口增长在20世纪70年代在都市区以外加速,远离城市. 这一趋势表明,人们正朝着农村生活方式和开放的乡村发展,而不仅仅是小城镇.

    科学领域:

    • 人口统计学 人口统计学
    • 社会学 社会学 社会学
    • 城市研究 城市研究

    背景情况:

    • 从历史上看,人口增长集中在大都市地区.
    • 近几十年来,人口分布模式发生了变化.
    • 了解这些人口变化对于城市和农村规划至关重要.

    研究的目的:

    • 分析20世纪70年代的人口增长趋势.
    • 确定人口分散的主要目的地,以超出大都市区.
    • 评估这些趋势对未来生活方式的影响.

    主要方法:

    • 分析了20世纪70年代的人口普查数据.
    • 对大都会地区内外人口增长率的比较研究.
    • 检查定居模式 (大都市与非大都市,小城镇与开放的乡村).

    主要成果:

    • 人口增长在20世纪70年代,大都市区以外的人口增长明显高于大都市区内的人口增长.
    • 人口分散主要是向开放的乡村,而不是小城镇.
    • 这种模式代表了已建立的历史人口趋势的逆转.

    结论:

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    Rapid Detection of Fecal Antigen of Helicobacter pylori Infection Based on Double Antibody Sandwich Detection Technology

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    Methods of Soil Resampling to Monitor Changes in the Chemical Concentrations of Forest Soils
    09:16

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    Published on: November 25, 2016

    Sampling Soils in a Heterogeneous Research Plot
    07:11

    Sampling Soils in a Heterogeneous Research Plot

    Published on: January 7, 2019

    Rapid Detection of Fecal Antigen of Helicobacter pylori Infection Based on Double Antibody Sandwich Detection Technology
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    Rapid Detection of Fecal Antigen of Helicobacter pylori Infection Based on Double Antibody Sandwich Detection Technology

    Published on: May 23, 2025

    • 20世纪70年代是人口重新分配的关键时期.
    • 有证据表明,人们正在向农村生活方式转变.
    • 对这些人口变化的持续监测对于政策制定至关重要.