Ch13-16 Summary

• Sample Statistics


  Variables in a sample or measures computed from sample data
• Population Parameters


  Variables in a population or measured characteristics of the population
• Descriptive Statistics


  Describe characteristics of populations or samples
• Descriptive Statistics


  • Number of people
  • Trends in employment
  • Data
• Inferential Statistics


  Make inferences about whole populations from a sample
• Frequency Distribution


  A set of data organized by summarizing the number of times a particular value of a variable occurs
• Percentage Distribution


  A frequency distribution organized into a table (or graph) that summarizes percentage values associated with particular values of a variable
• Probability


  The long-run relative frequency with which an event will occur
• Proportion


  The percentage of elements that met some criterion
• Top-Box Score


  Proportion of respondents who chose the most positive choice in a multiple choice question
• Mean


  A measure of central tendency; the arithmetic average
• Median


  A measure of central tendency that is the midpoint; the value below which half the values in a distribution fall
• Mode


  A measure of central tendency; the value that occurs most often
• Range


  The distance between the smallest and the largest values of a frequency distribution
• Deviation Scores


  Indicate how far any observation is from the mean
• Variance


  A measure of variability or dispersion. Its square root is the standard deviation
• Standard Deviation


  A quantitative index of a distribution's spread, or variability; the square root of the variance for a distribution
• Normal Deviation


  A symmetrical, bell-shaped distribution [normal curve] that describes the expected probability distribution of many chance occurrences
• Standardized Normal Deviation


  A purely theoretical probability distribution that reflects a specific normal curve for the standardized value, z
• Characteristics of a Standardized Normal Distribution

  • It is symmetrical about its mean
  • The mean identifies the normal curve's highest point (the mode) and the vertical line about which this normal curve is symmetrical
  • The normal curve has an infinite number of cases (it is a continuous distribution), and the area under the curve has a probability density equal to 1.0
  • The standardized normal distribution has a mean of 0 and a standard deviation of 1
• Standardized Values


  Used to compare an individual value to the population mean in units of the standard deviation
• Population Distribution


  A frequency distribution of the elements of a population
• Sample Distribution


  A frequency distribution of a sample
• Sampling Distribution


  A theoretical probability distribution of sample means for all possible samples of a certain size drawn from a particular population
• Standard Error of the Mean

  The standard deviation of the sampling distribution
• Central-Limit Theorem


  The theory that, as sample size increases, the distribution of sample means of size n, randomly selected, approaches a normal distribution
• Point Estimate


  An estimate of the population mean in the form of a single value, usually the sample mean
• Confidence Interval Estimate


  A specified range of numbers within which a population mean is expected to lie; an estimate of the population mean based on the knowledge that it will be equal to the sample mean plus or minus a small sampling error
• Confidence Level


  A percentage or decimal value that tells how confident a researcher can be about being correct; it states the long-run percentage of confidence intervals that will include the true population mean
• Random sampling error varies with samples of different sizes
• Increases in sample size reduce sampling error at a decreasing rate
• Factors in Determining Sample Size for Questions Involving Means

  • Variance (or Heterogeneity)
  • Magnitude of Error (Confidence Interval)
  • Confidence Level
• Sequential Sampling


  Conducting a pilot study to estimate the population parameters so that another, larger sample of the appropriate sample size may be drawn
• Coding


  The process of assigning a numerical score or other character symbol to previously edited data
• Codes


  Rules for interpreting, classifying, and recording data in the coding process; also, the actual numerical or other character symbols assigned to raw data
• Dummy Coding


  Numeric '1' or '0' coding where each number represents an alternate response such as 'female' or 'male'
• Effects Coding


  An alternative to dummy coding using the values of -1 and 1 to represent two categories of responses
• Descriptive Analysis


  The elementary transformation of raw data in a way that describes the basic characteristics such as central tendency, distribution, and variability
• Histogram


  A graphical way of showing a frequency distribution in which the height of a bar corresponds to the observed frequency of the category
• Tabulation


  The orderly arrangement of data in a table or other summary format showing the number of responses to each response category; tallying