Ch. 10 - Results and Conclusions
Monday, December 17, 2012 1:41 AM
PSYC2520:Introductionto Experimental Psychology
BeginningBehavioralResearch:A Conceptual Primer(7thed. 2012)Rosnow & Rosenthal
How is visualintegrityensuredwhen resultsaregraphed?
• Clarity (representing data in a way that is closely integrated with the numerical meaning),precision (representing results with the needed exactness and not
exaggerating numbers), and efficiency (presenting the numbers in a reasonably compact space so that the reader is encouraged to think about important details and
is not distracted by unnecessary ones) are important criteria of graphic integrity when we want to represent numerical data in a visual display
How arefrequenciesdisplayedin tables,bar graphs,and line graphs?
• A frequency distribution shows the number of times that each score or other unit of observation occurs in a set of data
○ Typically a bar graph, line graph, or table
• In a bar graph, the height of solid bars represents the number (frequency) of each score
○ The scale values are on the horizontal axis (X-axis or abscissa)
○ The frequency is on the vertical axis (Y-axis or ordinate)
Bar graphs are especially useful for representing categories of responses and frequencies (or proportions) within these categories
• Line graphs are an efficient way of graphing changes in the frequency (or proportion) of scores over time
How do stem-and-leafchartswork?
• In a stem-and-leaf chart, the original data are presented with any desired precision so that we can visually detect the symmetry, spread, and concentration of the
batch as well as any outliers
• A variation is the back-to-back stem-and-leaf chart
How arepercentilesused to summarizepartof a batch?
• A percentile locates a score in a distribution by defining the point at or below which a given proportion (or percentage) of the case falls
• The interquartile range is the distance between the 25th and 75th percentiles
• The median (Mdn or 50th percentile) is the midmost score of a distribution
How is an exploratorydata analysisdone?
• Confirmatory data analysis - hypothesis testing
• Exploratory data analysis - The use of simple arithmetic and visual techniques (such as the stem-and-leaf chart) to change our point of view by l