Chapter 9 - Descriptive statistics, significance levels, and hypothesis testing. After reading this chapter, you should be able to: Explain the concept of the normal curve, assess data for its distribution and compare it to the normal curve, create a frequency distribution and polygon for each variable in a dataset, compute and interpret the mean, median, and mode for each variable in a dataset,. | Descriptive statistics, significance levels, and hypothesis testing Chapter 9 Looking at dataset Normal curve Also known as bell curve A theoretical distribution of scores Majority of cases distributed around the peak in the middle Progressively fewer cases moving away form the middle Symmetrical – one side mirrors the other Mean, median, and mode have the same value Normal curve Positively skewed distribution Negatively skewed distribution Descriptive statistics Summary information for each variable Number of cases Central tendency Dispersion Used by researcher to describe variables Used in statistical tests to analyze differences and relationships between variables Number of cases Number of cases for which data are reported Represented by n or N n = 231 Cases may be people, speaking turns, episodes – any phenomenon studied Measures of central tendency Mean or M or Arithmetic mean or average Most sensitive to extreme scores Median or Mdn Middle of all scores on one variable Mode or | Descriptive statistics, significance levels, and hypothesis testing Chapter 9 Looking at dataset Normal curve Also known as bell curve A theoretical distribution of scores Majority of cases distributed around the peak in the middle Progressively fewer cases moving away form the middle Symmetrical – one side mirrors the other Mean, median, and mode have the same value Normal curve Positively skewed distribution Negatively skewed distribution Descriptive statistics Summary information for each variable Number of cases Central tendency Dispersion Used by researcher to describe variables Used in statistical tests to analyze differences and relationships between variables Number of cases Number of cases for which data are reported Represented by n or N n = 231 Cases may be people, speaking turns, episodes – any phenomenon studied Measures of central tendency Mean or M or Arithmetic mean or average Most sensitive to extreme scores Median or Mdn Middle of all scores on one variable Mode or Mo Score or scores that appear most often Measures of dispersion Describes the variability or spread of scores Should be reported with mean Range Highest to lowest score Standard deviation or sd If sd = 0, all scores are the same Larger the sd, the more the scores differ from the mean Standard deviation Standard deviations Theoretical normal curve is divided into equal standards The more normal a distribution of scores, the more this theoretical property applies of scores fall within +1 to –1 standards Using Descriptive statistics Reported in methods section of research report Mean, sd, range, and n should be reported for each variable Frequencies or f the number of times a particular value of a variable occurs Percentages or % often used to describe characteristics or attributes of participants Calculating -- Need calculator with square root key, spreadsheet program, or statistics program Researcher must select appropriate descriptive statistic and test Researcher must .
