Intro to Stats

• Statistics is a science that studies data
• Statistics involves processes from collecting, processing, analyzing, interpreting and communicating data.
• The word “statistics” actually comes from the word “state”— because governments have been involved in the statistical activities, especially the conduct of censuses either for military or taxation purposes.
• Five Stages of statistical investigation:

  1. Collection of Data
  2. Organization of Data
  3. Presentation of Data
  4. Analysis
  5. Interpretation of results
• DATA is a collection of facts from experiments, observations, sample surveys and censuses, and administrative reporting systems.
• The frequency of a particular data value is the number of times the data value occurs
• VARIABLE is any characteristic, number, or quantity that can be measured or counted.
• A variable may also be called a data item.
• QUALITATIVE variables, also called categorical variables
• Statistical variables have two classifications: Qualitative and Quantitative
• For questions about ideas, experiences and meanings, or to study something that can’t be described numerically, collect qualitative data.
• QUANTITATIVE variables, also called numerical variables.
• If you want to develop a more mechanistic understanding of a topic, or your research involves hypothesis testing, collect quantitative data
• Kinds of Quantitative Data: Discrete variable and Continuous variable
• DISCRETE variable is a variable that can take on a finite number of distinct values.
• CONTINUOUS variable is an uncountable number of potential values, regularly measurable amounts.
• Level of Measurements:

  *Nominal

  *Ordinal

  *Interval

  *Ratio
• Nominal scale is a variable that does not really have any evaluative distinction. One value is really not any greater than another.
• With nominal variables, there is a qualitative difference between values, not a quantitative one.
• Ordinal scale does have an evaluative connotation. One value is greater or larger or better than the other.  With ordinal variables, there is a qualitative difference between values, not a quantitative one
• Interval scale gives information about more or betterness as ordinal scales do, but interval variables have an equal distance between each value. Zero does not represent the absolute lowest value.
• Ratio scale has the same properties that an interval scale has except, with a ratio scaling, there is an absolute zero point.
• Types of variables: Dependent variable and independent variable
• Dependent variable - a factor, property, characteristics or attribute that is measured and made the object of analysis.
• Independent variable - a factor, property, attribute, characteristic or approach that is introduced, manipulated or treated to determine if it influenced or causes change on the dependent variable.
• Two Types of Statistics: Descriptive Statistics and Inferential Statistics
• Descriptive statistics is the term given to the analysis of data that helps describe, show or summarize data in a meaningful way
• Descriptive statistics do not allow us to make conclusions beyond the data we have analyzed or reach conclusions regarding any hypotheses we might have made. They are simply a way to describe our data.
• When we use descriptive statistics it is useful to summarize our group of data using a combination of tabulated description, graphical description and statistical commentary.
• With inferential statistics, you are trying to reach conclusions that extend beyond the immediate data alone.
• For instance, we use inferential statistics to try to infer from the sample data what the population might think.
• We use inferential statistics to make judgments of the probability that an observed difference between groups is a dependable one or one that might have happened by chance in this study.
• We use inferential statistics to make inferences from our data to more general conditions; we use descriptive statistics simply to describe what's going on in our data.