C3 Graphic Representation

• central tendency is a summary measure that attempts to describe a whole set of data with a single value that represents the middle or centre of its distribution.
• The proportion of area under a frequency curve between any two score points is equal to the relative frequency of cases between those points.
• normal curve is a distribution shape central to statistical work.
• To graph Qualitative Data, use The Bar Chart or the Pie Chart
• Pie charts are used when there are only a few categories and it’s important to see their proportions clearly.
• Quantitative data can be represented using histograms, dot plots, stem-and-leaf displays, boxplots, scatter diagrams, and line graphs.
• Bar Charts are used when there are many categories and it’s more useful to compare them side by side.
• A histogram is similar to a bar chart but uses continuous intervals rather than discrete ones.
• A bar chart shows how many people fall into different categories (qualitative) or have values within certain ranges (quantitative).
• Histograms can be used to show how often different values occur within an interval on a scale.
• Dot Plots show how many observations fall within certain ranges (or classes) of scores.
• Stem-and-Leaf Displays are similar to Dot Plots but they have more detail about the exact values of the observations.
• The Scale of the histogram: The rule of thumb is that the vertical axis should be roughly three-quarters the length of the horizontal. (Width and height are measured from the span of the graphed data, not the borders of the graph.)
• Proportional Area is used for comparing proportions (size, quantities, etc.) to provide a quick overview of the relative size of data without the use of scales.
• A box plot conveys important information about a distribution, particularly in terms of central tendency, variability, and shape.
• The box extends from the 25th percentile (or Q1, thefirst quartile) to the 75th percentile (or Q3, the third quartile).
• Graphic representation of the important features of a set of data makes frequency distribution easier to see.
• Scores usually are represented along the horizontal axis and frequencies (or relative frequencies) along the vertical axis.
• Scales should be selected so that the graph is somewhat wider than tall.
• Axes should be labeled and an informative title included.
• Frequency is represented by height in a histogram.
• Describe a frequency distribution in terms of three key characteristics: central tendency, variability, and shape.
• A variable is any characteristic, number, or quantity that can be measured or counted.
• Quantitative data refers to numerical values obtained from measurements or counts.
• Qualitative data refers to non-numerical information about objects or events.