Applied statistics | Actuarial science
In statistics, marketing and demography, a cohort is a group of subjects who share a defining characteristic (typically subjects who experienced a common event in a selected time period, such as birth or graduation). Cohort data can oftentimes be more advantageous to demographers than period data. Because cohort data is honed to a specific time period, it is usually more accurate. It is more accurate because it can be tuned to retrieve custom data for a specific study. In addition, cohort data is not affected by tempo effects, unlike period data. On the contrary, cohort data can be disadvantageous in the sense that it can take a long amount of time to collect the data necessary for the cohort study. Another disadvantage of cohort studies is that it can be extremely costly to carry out, since the study will go on for a long period of time, demographers often require sufficient funds to fuel the study. Demography often contrasts and . For instance, the total cohort fertility rate is an index of the average completed family size for cohorts of women, but since it can only be known for women who have finished child-bearing, it cannot be measured for currently fertile women. It can be calculated as the sum of the cohort's age-specific fertility rates that obtain as it ages through time. In contrast, the total period fertility rate uses current age-specific fertility rates to calculate the completed family size for a notional woman, were she to experience these fertility rates through her life. A study on a cohort is a cohort study. Two important types of cohort studies are: 1. * Prospective Cohort Study: In this type of study, there is a collection of exposure data (baseline data) from the subjects recruited before development of the outcomes of interest. The subjects are then followed through time (future) to record when the subject develops the outcome of interest. Ways to follow-up with subjects of the study include: phone interviews, face-to-face interviews, physical exams, medical/laboratory tests, and mail questionnaires. An example of a prospective cohort study is, for instance, if a demographer wanted to measure all the males births in the year 2018. The demographer would have to wait for the event to be over, the year 2018 must come to an end in order for the demographer to have all the necessary data. 2. * Retrospective Cohort Study: Retrospective Studies start with subjects that are at risk to have the outcome or disease of interest and identifies the outcome starting from where the subject is when the study starts to the past of the subject to identify the exposure. Retrospective use records: clinical, educational, birth certificates, death certificates, etc. but that may be difficult because there may not be data for the study that is being initiated. These studies may have multiple exposures which may make this study difficult. On the other hand, an example of a retrospective cohort study is, if a demographer was examining a group of people born in year 1970 who have type 1 diabetes. The demographer would begin by looking at historical data. However, if the demographer was looking at ineffective data in attempts to deduce the source of type 1 diabetes, the demographers results would not be accurate. (Wikipedia).
Covariance (1 of 17) What is Covariance? in Relation to Variance and Correlation
Visit http://ilectureonline.com for more math and science lectures! To donate:a http://www.ilectureonline.com/donate https://www.patreon.com/user?u=3236071 We will learn the difference between the variance and the covariance. A variance (s^2) is a measure of how spread out the numbers of
From playlist COVARIANCE AND VARIANCE
Covariance (3 of 17) Population vs Sample Variance
Visit http://ilectureonline.com for more math and science lectures! To donate:a http://www.ilectureonline.com/donate https://www.patreon.com/user?u=3236071 We will learn the difference and calculate the variance of a population and the variance of a sample of a population. Next video in
From playlist COVARIANCE AND VARIANCE
Covariance (8 of 17) What is the Correlation Coefficient?
Visit http://ilectureonline.com for more math and science lectures! To donate:a http://www.ilectureonline.com/donate https://www.patreon.com/user?u=3236071 We will learn what is and how to find the correlation coefficient of 2 data sets and see how it corresponds to the graph of the data
From playlist COVARIANCE AND VARIANCE
Covariance (14 of 17) Covariance Matrix "Normalized" - Correlation Coefficient
Visit http://ilectureonline.com for more math and science lectures! To donate:a http://www.ilectureonline.com/donate https://www.patreon.com/user?u=3236071 We will find the “normalized” matrix (or the correlation coefficients) from the covariance matrix from the previous video using 3 sa
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Populations, Samples, Parameters, and Statistics
Please Subscribe here, thank you!!! https://goo.gl/JQ8Nys Populations, Samples, Parameters, and Statistics
From playlist Statistics
Covariance Definition and Example
What is covariance? How do I find it? Step by step example of a solved covariance problem for a sample, along with an explanation of what the results mean and how it compares to correlation. 00:00 Overview 03:01 Positive, Negative, Zero Correlation 03:19 Covariance for a Sample Example
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This educational video delves into how you quantify a linear statistical relationship between two variables using covariance! #statistics #probability #SoME2 This video gives a visual and intuitive introduction to the covariance, one of the ways we measure a linear statistical relation
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