Presenting and interpreting bar charts, histograms and frequency polygons...
1. BAR CHARTS - usually used when the data is in categories (nominal or ordinal) or to illustrate the average scores from different samples. It consists of a series of vertical bars of equal width on the x-axis but varying height to indicate the frequency of each category (on the y-axis).
2. HISTOGRAMS - useful form of graphical representation that can be used when presenting continuous data on interval or ratio scales of measurement. A histogram consists of a series of vertical bars of equal width to represent each score or group of scores (class interval) presented on the x-axis. The height of each bar on the y-axis represents the frequency of occurance of each score or class interval.
3. FREQUENCY POLYGONS - particularly useful technique when it is necessary to compare 2 or more frequency distrubitions. Used as an alternative to the histogram. Can be drawn by linking the midpoints from the top of each bar contained in a histogram.
MEASURES OF CENTRAL TENDENCY...
THE MEAN - the arithmetic average of a set of data. Calculated by adding all the values together and dividing the total by the number of scores.
- makes use of all the available data.
- most powerful of the measures of central tendency available.