Presentation on theme: "Chapter 1 Getting Started Understandable Statistics Ninth Edition"— Presentation transcript:
1 Chapter 1 Getting Started Understandable Statistics Ninth Edition By Brase and BrasePrepared by Yixun ShiBloomsburg University of Pennsylvania
2 What is Statistics? Collecting data Organizing data Analyzing data Interpreting data
3 Individuals and Variables Individuals are people or objects included in the study.Variables are characteristics of the individual to be measured or observed.
4 VariablesQuantitative Variable – The variable is numerical, so operations such as adding and averaging make sense.Qualitative Variable – The variable describes an individual through grouping or categorization.
5 DataPopulation Data – The variable is part of every individual of interest.Sample Data – The variable is part of only some of the individuals of interest, i.e. of just a part of the population.
6 Levels of MeasurementNominal – The data that consist of names, labels, or categories.Ordinal – The data can be ordered, but the differences between data values are meaningless.
7 Levels of Measurement: Interval Interval – The data can be ordered and the differences between data values are meaningful.Ratio – The data can be ordered, differences and ratios are meaningful, and there is a meaningful zero value.
8 Critical ThinkingReliable statistical conclusions require reliable data.When selecting a variable to measure, specify the process and requirement for the measurement.Pay attention to the measurement instrument and the level of measurement.Are the data from a sample or from the entire population?
9 Two Branches of Statistics Descriptive Statistics: Organizing, summarizing, and graphing information from populations or samples.Inferential Statistics: Using information from a sample to draw conclusions about a population.
10 Sampling From a Population Simple Random Sample of size nEach member of the population has an equal chance of being selected.Each sample of size n has an equal chance of being selected.
11 Sampling Techniques Simple random sampling Inappropriate sampling (asking patrons in a mall to participate in a survey, soliciting volunteers in a newspaper ad to taste test a new snack food, etc)Systematic sampling
13 Critical ThinkingSampling frame – a list of individuals from which a sample is selected.Undercoverage – resulting from omitting population members from the sample frame.Sampling error – difference between measurements from a sample and that from the population.Nonsampling error – result of poor sample design, sloppy data collection, faulty measuring instruments, bias in questionnaires, and so on.
14 Guidelines For Planning a Statistical Study Identify individuals or objects of interest.Specify the variables.Determine if you will use the entire population. If not, determine an appropriate sampling methodDetermine a data collection plan, addressing privacy, ethics, and confidentiality if necessary.
15 Guidelines For Planning a Statistical Study Collect data.Analyze the data using appropriate statistical methods.Note any concerns about the data and recommend any remedies for further studies.
16 Census vs. SampleIn a census, measurements or observations are obtained from the entire population (uncommon).In a sample, measurements or observations are obtained from part of the population (common).
17 Observational StudyMeasurements and observations are obtained in a way that does not change the response or variable being measured.
18 Designed ExperimentsA treatment is applied to the individuals in the experiment in order to observe a potential effect on the variable being measuredDesigned experiments are used to pin down a cause-and-effect relationship.To measure the effect of a treatment, statisticians may break the individuals into treatment group and control group.
20 SurveysCollecting data from respondents through interviews, phone conversations, internet polls, mail polls, etc…Non-response: Respondents cannot be contacted or refuse to answer.Voluntary response surveys: May be biased due to strong opinions held by those willing to participate.Survey results usually cannot pin down a cause-and-effect relationship.