chapter 2

• what are descriptive statisitcs?

  methods used to provide a concise description of a collection of quantitative information.
• what are inferential statistics?

  methods used to make inferences from observations of a small group of people known as a sample to a larger group of individuals known as a population.
• what is a nominal scale of measurement?

  naming but does not indicate quantity of something (no magnitude, equal intervals or absolute 0) e.g., football jersey numbers
• what is an ordinal scale of measurement?

  ranking of individuals or objects in order. (has magnitude, no equal intervals, no absolute 0) e.g., college rankings, ordering people by height.
• what is interval scale of measurement?

  type of data that is measured along a scale where each point is equally spaced from the others. (has magnitude and equal intervals, no absolute 0) (used for average, most tests in psych are interval) e.g., temperate between 33 and 34 is the same as the temperature between 76 and 77.
• what is ratio scale of measurement?

  measures on a continuous scale, with an equal distance between adjacent values. (has magnitude, equal intervals, absolute 0) e.g., someone's weight
• what does positive skew mean?

  positive skew means that the tail of the distribution is longer on the right side, indicating that the majority of the data is concentrated on the left side.
• what does negative skew mean?

  negative skew mean that the tail of the distribution is longer on the left side, indicating the majority of the data is concentrated on the right side.
• what are percentile?

  specific scores or points within a distribution; they divide the total frequency for a set of observations into hundredths; percentile ranks indicate the particular score.
• what is the mean?

  the average score in a distribution; calculated by adding the total scores and divide the sum by the numbering of cases.
• what is the standard deviation?

  the average around the mean; how much a score deviates from the mean.
• what is variance?

  the average squared deviation around the mean.
• what is included in distributions?

  mean, standard (average) deviations (from the mean); deviations from scores will always be positive or negative [above the mean or below the mean]. e.g., average height is 66 inches --> so 63 inches has a standard deviation of -3 because it is 3 inches below the mean.
• what are z-scores?

  the number of standard deviations that someone is away from the mean; standardized measure (everyone has a z-score); -z score is below the mean +z is above the mean; z score = 0 the person is at the mean.
• what are norms?

  the average performance; refers to the performance by defined groups on particular tests; allows for comparisons
• what is within group norming?

  comparing an individual's performance to the performance of others within the same group; made illegal in 1991 civil rights act.
• what is norm referenced testing?

  comparing an individual's performance to the performance of a group (comparison with other test takers). e.g., comparing a females state math test score to only females who also took that state math test.
• what are criterion referenced testing?

  comparisons with some standard; if everyone performs above a certain standard then that's the score they get; "not competing with others"
• what are abitrary cut scores?

  not much meaning to them (made up); e.g., cut scores, score above a 90 or above earns an A.