Lesson 1

• Descriptive Statistics


  comprises those methods concerned with collecting and describing a set of data as to yield meaningful information.
• Inferential statistics


  comprises those methods concerned with analysis of subset of data leading to predictions or inferences about the entire set of data.
• Descriptive Statistics


  Academic records of the graduating classes during the past 5 years in a certain university show that 72% of the entering freshman eventually graduated
• Inferential statistics


  If you are a member of the present freshman class and conclude from this study that your chances of graduating are better than 70%, you have made a statistical inference that is subject to uncertainty.
• Population


  consists of the total collection of observations. It is a groups or aggregates of people, animals, objects, materials, happenings or things of any form.
• Population


  consist of the totality of observations with which we are concerned
• Sample


  is a subject of measurement taken from the population. It is a few members of the population to represent their characteristics.
• sample

  a subset of the population
• Parameter


  any numerical value describing a characteristic of a population
• Parameter


  use to represent a certain population
• Statistics


  any numerical value describing a characteristic of a sample
• Statistics


  use to give information about unknown values in the corresponding population
• Variable


  refers to the characteristics or property whereby members of the group or set vary from another
• Variable


  A characteristic or information of interest that is observable or measurable from every individual or object under consideration.
• Types of Variable

  Qualitative or Categorical

  Quantitative or Numerical varia
• Qualitative or Categorical Variable


  is a variable is a variable that Measures a quality or characteristics
• Quantitative or Numerical Variable


  Measures a numerical quantity or amount, it Answers the question “how much” or “how many”.
• Quantitative variable is either

  Discrete or Continuous
• Discrete


  assumes only a finite, specific values or countable number of values
• Continuous Variable


  assumes infinitely many values corresponding to the points on a line interval
• Categorical

  Examples:

  Marital Status

  Political Party

  Eye Color
• Discrete


  Examples:

  Number of Children

  Defects per hour
• Continuous


  Examples:

  Number of Children

  Defects per hour
• Variable Can be either

  Dependent

  Independent Variable
• Dependent Variable


  Is sometimes called criterion variables
• Independent Variable


  is sometimes called a predictor variable or a variable that can be controlled or manipulated.
• Suppose the investigator is interested in the relationships between two variables: the effect of information about the gender of a job applicant on hiring decisions made by personnel managers. The Hiring decision is what variable?

  Dependent Variable
• Suppose the investigator is interested in the relationships between two variables: the effect of information about the gender of a job applicant on hiring decisions made by personnel managers. The gender of the applicant is a what variable?

  Independent Variable
• Constant


  refers to the property whereby the members of the group do not differ from one another.
• Levels of Measurement

  • Nominal Scale
  • Ordinal Scale
  • Interval Scale
  • Ratio Scale
• Nominal Scale


  used with variables that are qualitative in nature.

  The data collected are simply labels, categories or nameless without any implicit or explicit ordering of the categories or explicit ordering of the labels.

  The observations or subjects belong to the same category.

  It is the lowest level of measurement. Nominal scale does not possess any of the attributes of magnitude, equal interval or absolute zero point.
• Nominal Scale

  1. Sex/ Gender
  2. The complexion of students
  3. Hair Color of students
• Ordinal Scale


  has a relative low level of property of magnitude, but it does not have the property of equal intervals between the adjacent units. This is concerned with the ranking or order of the objects measured. The level of measurement is higher than nominal.
• Ordinal Scale


  Example

  1. Winners of a contest
  2. Faculty Rank
  3. Military Rank
• Interval Scale


  has its property of magnitude and equal interval between two adjacent units, but it does have an absolute zero point. The data collected can be ordered or rank. The unit measurement is constant. The level of measurement is higher than the ordinal.
• Interval Scale


  Example

  Temperature in Celsius scale

  IQ of zero does not mean total absence of knowledge
• Ratio Scale


  is the highest level of measurement scale. It has all the properties of an interval scale, that is, it has magnitude and equal intervals plus the absolute zero point. There is a constant size interval between each successive unit on the measurement scale. Furthermore, there is a physical significance to this zero.
• Ratio Scale

  1. The reaction time to a particular drug
  2. The number of visits to a Doctor,
  3. The weight loss of on diet individual,
  4. The average score of CAT score of CAS students