© The McGraw-Hill Companies, Inc., by Marc M. Triola & Mario F. Triola SLIDES PREPARED BY LLOYD R. JAISINGH MOREHEAD STATE UNIVERSITY MOREHEAD KY (with modifications by DGE Robertson) Biostatistics for the Biological and Health Sciences

1-2 Chapter 1 Introduction WCB/McGraw-Hill © The McGraw-Hill Companies, Inc., 1998

© The McGraw-Hill Companies, Inc., Outline 1-1 Introduction 1-2 Types of Data Data Collection and Sampling Techniques 1-4 Data Collection and Sampling Techniques 1-5 Computers and Calculators

© The McGraw-Hill Companies, Inc., Objectives Demonstrate knowledge of all statistical terms. Differentiate between the two branches of statistics. Identify types of data.

© The McGraw-Hill Companies, Inc., Objectives Identify the measurement level for each variable. Identify the four basic sampling techniques.

© The McGraw-Hill Companies, Inc., Introduction Statistics Statistics consists of conducting studies to collect, organize, summarize and analyze data and to draw conclusions

© The McGraw-Hill Companies, Inc., Descriptive and Inferential Statistics Data Data are the values (measurements or observations) that the variables can assume. random variables Variables whose values are determined by chance are called random variables.

© The McGraw-Hill Companies, Inc., Descriptive and Inferential Statistics data set. A collection of data values forms a data set. data valuedatum Each value in the data set is called a data value or a datum.

© The McGraw-Hill Companies, Inc., Descriptive and Inferential Statistics Descriptive statistics Descriptive statistics consists of the collection, organization, summation and presentation of data.

© The McGraw-Hill Companies, Inc., Descriptive and Inferential Statistics population A population consists of all subjects (human or otherwise) that are being studied. A measurable characteristic of a population is called a parameter.

© The McGraw-Hill Companies, Inc., Descriptive and Inferential Statistics sample A sample is a subgroup of the population. A measurable characteristic of a sample is called a statistic.

© The McGraw-Hill Companies, Inc., Descriptive and Inferential Statistics Inferential statistics Inferential statistics consists of generalizing from samples to populations, performing hypothesis testing, determining relationships among variables, and making predictions.

© The McGraw-Hill Companies, Inc., Variables and Types of Data Qualitative variables Qualitative variables are variables that can be placed into distinct categories, according to some characteristic or attribute. For example, gender (male or female).

© The McGraw-Hill Companies, Inc., Variables and Types of Data Quantitative variables Quantitative variables are numerical in nature and can be ordered or ranked. Example: age is numerical and the values can be ranked.

© The McGraw-Hill Companies, Inc., Variables and Types of Data Discrete variables Discrete variables assume values that can be counted. Continuous variables Continuous variables can assume all values between any two specific values. They are obtained by measuring.

© The McGraw-Hill Companies, Inc., Variables and Types of Data nominal level of measurement The nominal level of measurement classifies data into mutually exclusive (nonoverlapping), exhausting categories in which no order or ranking can be imposed on the data.

© The McGraw-Hill Companies, Inc., Variables and Types of Data ordinal level of measurement The ordinal level of measurement classifies data into categories that can be ranked; precise differences between the ranks do not exist.

© The McGraw-Hill Companies, Inc., Variables and Types of Data interval level of measurement The interval level of measurement ranks data; precise differences between units of measure do exist; there is no meaningful zero.

© The McGraw-Hill Companies, Inc., Types of Data ratio level of measurement The ratio level of measurement possesses all the characteristics of interval measurement, and there exists a true zero (i.e., a value that means there is nothing left of the measure).

© The McGraw-Hill Companies, Inc., 2000 In SPSS the Interval and Ratio levels are combined as Scale level data Types of Data

© The McGraw-Hill Companies, Inc., Data Collection and Sampling Techniques Data can be collected in a variety of ways. One of the most common methods is through the use of surveys or polls. Surveys can be done by using a variety of methods: Examples are telephone, online questionnaires, personal interviews, census records, and direct observations.

© The McGraw-Hill Companies, Inc., Data Collection and Sampling Techniques To obtain samples that are unbiased, statisticians use several methods of sampling. Random samples Random samples are selected by using chance methods or random numbers (where every datum has equal probability of being chosen, each time. Be sure not to select same datum twice).

© The McGraw-Hill Companies, Inc., Data Collection and Sampling Techniques Systematic samples Systematic samples are obtained by numbering each value in the population (1 to N) and then selecting the k th value. First select sample size (n) then select every k=N/n th member.

© The McGraw-Hill Companies, Inc., Data Collection and Sampling Techniques Stratified samples Stratified samples are selected by dividing the population into groups (strata) according to some characteristic (e.g., sex, age range, blood type) and then taking proportional samples from each group.

© The McGraw-Hill Companies, Inc., Data Collection and Sampling Techniques Cluster samples Cluster samples are selected by dividing the population into groups and then taking samples of the groups (e.g., locales, schools, countries). This method is more economical than using the whole population.

© The McGraw-Hill Companies, Inc., Data Collection and Sampling Techniques Convenience samples Convenience samples are when subjects are selected for convenience. (Often used in student research projects or by advertisers.)

© The McGraw-Hill Companies, Inc., Calculators Calculators or smartphone apps make some statistical tests and numerical computations easier. The some calculators/apps perform 2- variable statistical calculations. Must learn how to enter and perform statistical functions on your calculator/app.

© The McGraw-Hill Companies, Inc., Computers and Calculators Computers can perform more advanced statistical tests. SPSS Many statistical packages are available. Examples are SPSS, SAS, and MINITAB also Excel and QuattroPro. Input and output from computer must understood and interpreted by a qualified statistician (soon to be you!).