Lesson 5

• point about which the scores tend to cluster around

  measure of central tendency
• a value which gives a summary of the characteristics of a given set of data

  measure of central tendency
• three measures of central tendency

  • mean
  • median
  • mode
• sum of all the given values or items in a distribution divided by the number of values or items summed

  arithmetic mean or mean
• refers to data not yet organized into frequency distribution

  ungrouped data
• refers to a set of data presented in the form of frequency distribution

  grouped data
• grouped data are so structured or classified into categories for better presentation and analysis
• two types of data in calculating the mean

  • grouped data
  • ungrouped data
• denotes the sum of all the numbers in a given set

  summation notation
• entire group under consideration

  population
• any subset of the population

  sample
• often used when some data are more important than others

  weighted mean
• a point in the distribution of scores at which 50 percent of the scores fall below and 0 percent of the scores fall above

  median
• it is a value that divides an array into two equal parts

  median
• most frequently appearing score or group of scores appearing in a distribution

  mode
• refers to the extent to which the scores on a quantitative variable in a distribution are spread out

  variability
• most common measure of variability?

  standard deviation
• the mean of the squared deviations of the observations from the mean

  variance
• a measure of variability that considers the position of each observation relative to the mean of the set of scores

  variance
• the standard deviation is defined as the positive square root of the variance
• among the many continuous distributions used in the entire theory of statistics, normal distribution is by far the most important
• It has been observed that the weights of a large number of individuals tend to be approximately normally distributed
• a similar observation holds true for the distribution of IQs (intelligence quotients) of people
• a mathematically theoretical concept or model that depicts tendency that the scores always tend to be distributed around the average

  normal distribution
• normal distribution is sometimes called the Gaussian Distribution
• A normal distribution forms a bell-shaped curve that is symmetric about a vertical line through the mean of the data
• the number of standard deviations by which the value of a raw score is above or below the mean value of what is being observed or measured

  standard score
• standard score is also called?

  z-score
• z-score gives you and idea of how far from the mean a data point is
• standard score refers to a kind of transformed score to the mean and standard deviation of a distribution
• we simply obtain areas under any normal curve by performing a simple change of fscale called the standard score
• the mean is the center of the normal distribution while the standard deviation is the amount of spread of the scores