Bluman_11e_PPT_Ch01_01_ACCESS.pptx

Because learning changes everything. ® Chapter One The Nature of Probability and Statistics Section 1 Descriptive and Inferential Statistics © McGraw Hill LLC. All rights reserv...

Because learning changes everything. ® Chapter One The Nature of Probability and Statistics Section 1 Descriptive and Inferential Statistics © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.  Learning Objectives Demonstrate knowledge of statistical terms. Differentiate between the two branches of statistics. © McGraw Hill LLC Monkey Business Images/Shutterstock 2  What is Statistics? Statistics is the science of conducting studies to. collect, organize, summarize, analyze, and. draw conclusions from data. In this section we will learn. The different branches of statistics. What are data. © McGraw Hill LLC 3  Variables and Data A variable is a characteristic or attribute that can assume different values. The values that a variable can assume are called data. A collection of data is a data set, and each individual value is called a data value or datum. A variable whose values are determined by chance are called random variables. An insurance company studies its records over the past several years (data) and determines that, on average, 3 out of every 100 automobiles insured were involved in accidents in a 1-year period. There is no way to predict the specific automobiles that will have accidents. The number of accidents in one year is a random variable. © McGraw Hill LLC 4  Populations A population consists of all subjects (human or otherwise) that are being studied. When data is collected from every subject in the population, it is called a census. The United States conducts a census every ten years as mandated in the Constitution, but it is a time-consuming and expensive process. Most of the time, it is not possible to use the entire population for a statistical study, therefore, researchers use samples. © McGraw Hill LLC 5  Samples A sample is a group of subjects selected from a population. If the subjects in the sample are properly selected, they will be representative of the population as a whole. This way, studying the sample helps us learn about the population of interest. If the subjects are not well selected, the sample will be biased because the subjects in the sample are not representative of the population as a whole. We will study how to properly select a sample in Section 1-3. © McGraw Hill LLC 6  Descriptive Statistics Descriptive statistics consists of the collection, organization, summarization, and presentation of data. The census is an example of descriptive statistics. Data are collected from everyone in the United States, from which average ages, household sizes, and other demographic information is determined. This information is presented in tables of values, but also in charts and graphs, in order to effectively summarize and present the information. © McGraw Hill LLC 7  Inferential Statistics Inferential statistics consists of generalizing from samples to populations, performing estimations and hypothesis tests, determining relationships among variables, and making predictions. After taking a sample, descriptive statistics is done to summarize and present the data collected about the sample. However, the goal of taking a sample is to draw conclusions about the population as a whole. In order to effectively make these inferences, we must understand probability, the chance of an event occurring. For example, suppose we are testing light bulbs for defects, and 3 out of the 10 we sample are defective. How likely is that to happen if the light bulbs are generally non-defective? © McGraw Hill LLC 8  Hypothesis Testing Hypothesis testing is a process for evaluating claims about a population, based on information obtained from a sample. When we tested the lightbulbs before, we may have assumed that 1% of all lightbulbs are defective, due to chance. However, 30% of the lightbulbs in our sample were defective! Hypothesis testing gives us a rigorous way to determine if we can conclude that the manufacturing process needs adjusting, based on this information. Statistics can also be used to find relationships between variables. For example, there is a relationship between the heights of parents and the heights of children: taller parents have taller children. © McGraw Hill LLC 9  Descriptive or Inferential? A pharmaceutical company wants to test a new drug to prevent heart attacks. They, in cooperation with a local hospital, find 300 people with heart disease, give half of them the new drug, and give the other half a placebo (a substance with no medical benefit or harm). 50 of the people who received the new drug had a heart attack in a 6 month period, versus 90 of the people who received the placebo. “The new drug prevented almost 50% of heart attacks in the sample” is descriptive statistics. The rate of heart attacks among people who got the new drug was 5/9 the rate among people who didn’t. “The new drug reduces the risk of heart attacks by 50%” is inferential statistics. It is generalizing the result from the sample to make a conclusion about the population. © McGraw Hill LLC 10  End of Main Content Because learning changes everything. ® www.mheducation.com © McGraw Hill LLC. All rights reserved. No reproduction or distribution without the prior written consent of McGraw Hill LLC.