Final answer:
In single-subject design data analysis, three parameters - level, trend, and variability - are crucial for visual assessment. Graphs should be critically analyzed and chosen based on their ability to represent aspects of the data such as comparisons, trends, or relationships.
Step-by-step explanation:
When analyzing data in single-subject designs, three key parameters are often used to visually assess the data presented in graphs. These parameters are level, trend, and variability. Level refers to the value on the vertical axis around which a series of data points converge. Trend is about the direction and steepness of data points on a graph, which can indicate an increasing, decreasing, or stable pattern over time. Variability represents the degree to which data points diverge from the level, indicating the consistency or spread of data around the trend line.
Graphs should always be viewed with a critical eye, as they can be influenced by several factors such as the data selected, time frame considered, grouping of data, axis scaling, and whether the y-axis starts at zero. Each type of graph, like a bar chart, line graph, or scatter plot, has its appropriate uses depending on what aspect of the data one wants to emphasize or explore.
For example, a bar chart is most commonly used to compare different groups or categories. A line graph best illustrates trends or changes over time in continuous data. A scatter plot is appropriate for examining the relationship between two quantitative variables, often used to identify correlation patterns or outliers.