Chapter 3: Visual Displays of Data

What is the formula for relative frequency?

Relative Frequency = Frequency in Category/Total Frequency

What are the characteristics of a histogram?

1. A histogram is a bar graph for quantitative data(at the interval or ratio level of measurement). 2. The bars have a natural order and the bar widths have specific meaning.

What are the characteristics of a line chart?

1. A line chart shows the data value for each category as a dot, with the dots connected by lines. 2. For each dot, the horizontal position is in the center of the category it represents, and the vertical position is the data value for the category.

What are the characteristics of a pie chart?

1. It is a circle divided so that each wedge represents the relative frequency of a particular category. 2. The entire pie represents the total relative frequency of 100%.

What are the characteristics of a line plot?

1. It is a variation of a bar graph. 2. It uses dots to represent frequencies instead of bars. 3. Each dot represents one data value. 4. Like bar graphs, they are also qualitative. Actual Definition: A dotplot is similar to a bar graph, except each individual data value is represented with a dot.

Which types of graphs are for qualitative data?

Bar Graph, Dotplot, Pareto Chart, and Pie Chart are all for Qualitative Data (Categorical Data).

Which types of graphs are for quantitative data?

Histogram and Line Charts are for Quantitative Data.

Why should we keep track of scaling in graphs?

If the y-axis goes from 1-100, when the data values only go from 20-25, the data will look much less significant than a different graph with a y-axis that goes from 20-25. Depending on how one writes the y-axis, it can either exemplify a trend, or erase it mistakenly.

What are the characteristics of a Pareto chart?

It is a bar graph with the bars arranged in frequency order. Pareto charts make sense only for data at the nominal level of measurement.

What is the cumulative frequency (of any category)?

It is the number of data values in that category and all preceding categories. For example, in a data set of 20 values, it would be 20

What is the relative frequency (of any category)?

It is the proportion (or percentage) of the data values that fall in that category. For example, 1/20 would be 5%.

What does a frequency table summarize?

It summarizes the distribution of data.

What do the two columns in a basic frequency table include?

One column lists all the categories of data, and the other column lists the frequency of each category, which is the number of data values in the category.

Why should we keep track of % change in graphs?

Two graphs can have the same data, and a different outcome/trends due to different titles. For example, one graph showed the percentage increases for college tuition across the years. Another graph showed the prices for college tuition across the years. The graphs looked very different, but this was due to the fact that the first graph showed the data to be very up and down, because even though the % increases were always increases, they weren't always the same increase. The second graph did not have this trend because every year, it showed the college prices increasing, which they did. It just didn't show how much the prices changes percentage-wise, and instead showed a general idea of college prices increasing in general.

What are the characteristics of a bar graph?

1. It is one of the simplest ways to show a distribution. 2. They are used for qualitative data. 3. Each bar represents the frequency (or relative frequency, depending on the data) of each category. 4. The higher the frequency, the higher the bar is for that category. 5. The bars in a bar graph can either be horizontal or vertical. Actual Definition: A bar graph consists of bars representing frequencies (or relative frequencies) for particular categories. The bar lengths are proportional to the frequencies.

What are the characteristics of a time-series graph?

1. It represents a trend over the course of time. 2. The x-axis can be time/year/months/etc.