1 / 8

Introduction to Sampling and Descriptive Statistics in Scientific Research

This chapter introduces the essentials of sampling and descriptive statistics, emphasizing the importance of statistics in understanding uncertainty in repeated measurements and drawing reliable conclusions from experimental data. Key concepts include the definitions of populations and samples, the methods of simple random sampling (SRS), and the implications of sampling variation. Additionally, it explores the types of data (numerical and categorical) and fundamental summary statistics, including mean, variance, and standard deviation, which form the foundation for analyzing and interpreting data in scientific research.

eurydice-charis
Télécharger la présentation

Introduction to Sampling and Descriptive Statistics in Scientific Research

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 1: Sampling and Descriptive Statistics

  2. Why Statistics? • Uncertainty in repeated scientific measurements • Drawing conclusions from data • Designing valid experiments and draw reliable conclusions

  3. Section 1.1: Sampling Definitions: • A population is the entire collection of objects or outcomes about which information is sought. • A sample is a subset of a population, containing the objects or outcomes that are actually observed. • A simple random sample(SRS) of size n is a sample chosen by a method in which each collection of n population items is equally likely to comprise the sample, just as in the lottery.

  4. Simple Random Sampling • A SRS is not guaranteed to reflect the population perfectly. • SRS’s always differ in some ways from each other, occasionally a sample is substantially different from the population. • Two different samples from the same population will vary from each other as well. • This phenomenon is known as sampling variation.

  5. Definition: A conceptual population consists of all the values that might possibly have been observed. For example, a geologist weighs a rock several times on a sensitive scale. Each time, the scale gives a slightly different reading. Here the population is conceptual. It consists of all the readings that the scale could in principle produce. More on SRS

  6. The items in a sample are independent if knowing the values of some of the items does not help to predict the values of the others. Items in a simple random sample may be treated as independent in most cases encountered in practice. The exception occurs when the population is finite and the sample comprises a substantial fraction (more than 5%) of the population. SRS (cont.)

  7. Types of Data • Numerical or quantitative if a numerical quantity is assigned to each item in the sample. • Height • Weight • Age • Categorical or qualitativeif the sample items are placed into categories. • Gender • Hair color • Zip code

  8. Section 1.2: Summary Statistics • Sample Mean: • Sample Variance: • Sample standard deviation is the square root of the sample variance. • If X1, …, Xnis a sample, and Yi = a + b Xi ,where a and b are constants, then • If X1, …, Xnis a sample, and Yi = a + b Xi ,where a and b are constants, then Segue…

More Related