15. presentation of quantitative data

how can quantitative data be presented

• tables

• bar charts

• histograms

• scattergrams

tables

one way is the form of a summary table

• when tables appear in the results section of a report they are not merely raw scores, but have been converted to descriptive statistics

• it is standard practice to include a summary paragraph beneath explaining the numbers and drawing conclusions

bar charts

a type of graph in which the frequency of each variable is represented by the height of the bars

• data is divided into categories, discrete data

• bars are separated to denote you are dealing with separate conditions

histograms

a type of graph where the area of each bar represents the frequency

• the x axis must start at a true zero and the scale is continuous

• the y axis represents the frequency within each interval, if there was a zero frequency the interval remains but without a bar

scattergrams

a type of graph that represents the strength and discretion of the relationship between co variables in a correlational analysis

• each axis has a co variable

what is a normal distribution

a symmetrical spread of frequency data that forms a bell shaped pattern

• the mean, median and mode are all located at the highest peak

• the tails of the curve extend outwards and never touch the x axis as more extreme scores are always theoretically possible

what is a skewed distribution

a spread of frequency data that is not symmetrical, where the data clusters to one end

what is a positive skew

a type of frequency distribution in which the long tail is on the positive (right) side of the peak and most of the distribution is concentrated on the left

• mode is highest, then median, then mean

what is a negative skew

a type of frequency distribution in which the long tail is on the negative (left) side of the peak and most of the distribution is concentrated on the right

• mean, then median and then mode