Chapter 1 Overview Created by Tom Wegleitner, Centreville, Virginia Slide 1 11 Statistics Overview Slide 2
A. Statistics is the science of conducting studies to: Collect Organize Summarize Analyze Draw Conclusions from data Slide 3 22 B. Where do you use Statistics? Sports Business Research Public Health Slide 4
C. Why do we use Statistics? To be able to read and understand statistical studies. To Conduct Research. To become a better consumer and citizen. Slide 5 33 D. Basic Vocabulary Variable a characteristic or attribute of interest that can assume different values. It is the question asked. Data the values the variables have assumed (answers to the questions). Population all subjects of interest to the study. Sample a part of the population. Census collection of data from every member of the population. Slide 6
Parameter a numerical measurement describing some characteristic of the population. (Ex. Mean of the population) Statistic a numerical measurement describing some characteristic of the sample. (Ex. Mean of the sample) Slide 7 44 Ex 1. There are 482 students in Grant High School. 23% of those students are juniors.. Ex. 2 Based on a sample of 75 students 25% prefer to start school at 8:40 AM instead of 7:40 AM. Slide 8
E. Types of Variables 1. Qualitative Data: Data can be placed in distinct categories, according to some characteristic or attribute. Ex. Hair color Gender TV ownership Do you own a car? Employment status(full time, part time, not employed) Social Security Number License plate number Computer account number Slide 9 55 2. Quantitative Data: Data are numerical, representing counts or measurements that can be ordered or ranked. Ex. How many children do you have? Heights of basketball players Place finished in a race. Data values can be used to find the average, standard deviation, variance, etc. Slide 10
2 Types of Quantitative Data Discrete counts or data space between its possible values. Ex. Shoe size Continuous measures or data that can assume an infinite number of values between two endpoints. Ex. Foot length Slide 11 66 Identify each of the following variables as Qualitative; Quantitative, discrete; Quantitative, continuous Eye color Computer Password Shoe size Shirt size (S, M, L) Shirt size (10, 12,14, etc.) License Plate Number Zip code Weight Height Time to drive to school Qualitative Quantitative Discrete Quantitative Continuous Slide 12
F. Levels of Measurement Nominal only classifies data into mutually exclusive (non-overlapping), exhausting categories in which no order or ranking can be imposed on the data. Ex. SS# Ordinal classifies data into categories that can be ranked; however, precise differences between the ranks do not exist. Ex. Shirt size (S, M, L) Interval ranks the data with precise differences between the data values; however, there is no meaningful zero. Ex. Shoe size Ratio possesses all characteristics of interval measurement and a true zero. Ex. Foot length Slide 13 77 Identify each variable as nominal, ordinal, interval or ratio. Zip code Grade Eye color Rating Ranking Weight Gender IQ SAT score Height Temperature (C, F) Time Nominal Ordinal Interval Ratio Slide 14
The chart shows the number of job-related injuries for each of the transportation industries for 1998. Industry Number of Injuries Railroad 4520 Intercity 5100 Subway 6850 Trucking 7144 Airline 9950 1. What are the variables under study? 2. Classify each of the variables as Quantitative, continuous; Quantitative, discrete; or Qualitative 3. Identify the level of measurement for each variable. 4. The railroad is shown as the safest transportation industry. Does that mean railroads have fewer accidents that the other industries? 5. What factors other than safety influence a person s choice of transportation? Slide 15 88 1. What are the variables under study? 2. Classify each of the variables as Quantitative, continuous; Quantitative, discrete; or Qualitative 3. Identify the level of measurement for each variable. Slide 16
4. The railroad is shown as the safest transportation industry. Does that mean railroads have fewer accidents that the other industries? 5. What factors other than safety influence a person s choice of transportation? Slide 17 99