Chapter 10 - Descriptive statistics. After reading this chapter, you should be able to: Select existing or design appropriate questionnaire items and response sets, use open and closed questions appropriately, pretest the method of data collection, collect the data in an honest and ethical manner, analyze the data completely and appropriately, draw conclusions that do not overstate the limitations of your data or sample, present the data to others in an appropriate fashion,. | 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 Looking at a 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 Skewed Distributions Curve is asymmetrical Positively skewed curve – very few high scores Negatively skewed curve – very few low scores 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 . | 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 Looking at a 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 Skewed Distributions Curve is asymmetrical Positively skewed curve – very few high scores Negatively skewed curve – very few low scores 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 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 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 Application of Descriptive Statistics Reported in methods section of research report Mean, sd, range, and n should be reported for each variable Frequencies – the number of times a particular value of a .
