Chapter 10 - 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,. | Chapter 10 Descriptive Statistics Numbers One tool for collecting data about communication phenomena Capture quality, intensity, value, or degree Only meaningful if they are interpreted Operationalizations specify how data are collected and become numerical Copyright c 2001 The McGraw-Hill Companies, Inc. Looking at a Data Set Copyright c 2001 The McGraw-Hill Companies, Inc. 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 Copyright c 2001 The McGraw-Hill Companies, Inc. Normal Curve Copyright c 2001 The McGraw-Hill Companies, Inc. Skewed Distributions Curve is asymmetrical Positively skewed curve – very few high scores Negatively skewed curve – very few low scores Copyright c 2001 The McGraw-Hill Companies, Inc. Descriptive Statistics Summary . | Chapter 10 Descriptive Statistics Numbers One tool for collecting data about communication phenomena Capture quality, intensity, value, or degree Only meaningful if they are interpreted Operationalizations specify how data are collected and become numerical Copyright c 2001 The McGraw-Hill Companies, Inc. Looking at a Data Set Copyright c 2001 The McGraw-Hill Companies, Inc. 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 Copyright c 2001 The McGraw-Hill Companies, Inc. Normal Curve Copyright c 2001 The McGraw-Hill Companies, Inc. Skewed Distributions Curve is asymmetrical Positively skewed curve – very few high scores Negatively skewed curve – very few low scores Copyright c 2001 The McGraw-Hill Companies, Inc. Descriptive Statistics Summary information for each variable Number of cases Central tendency Dispersion Helps researcher describe variables in research report Used in statistical tests to analyze differences and relationships between variables Copyright c 2001 The McGraw-Hill Companies, Inc. 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 Copyright c 2001 The McGraw-Hill Companies, Inc. Measures of Central Tendency Mean Arithmetic mean or average Most sensitive to extreme scores Median Middle of all scores on one variable Mode Score or scores that appear most often Copyright c 2001 The McGraw-Hill Companies, Inc. 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 Copyright c 2001 The McGraw-Hill .
