presentation of quantitative data

Question 1

how is data summarised in a table?

Answer 1

• quantitative data (raw scores) is converted into descriptive statistics (eg. mean) that can be summarised in a table
• comments / conclusions are then included in a summary paragraph

Question 2

when are bar charts used?

Answer 2

• to easily display the difference in mean values
• used for discrete data (can’t be divided into smaller categories eg. days of week)
• IV goes on x-axis, shows categories of various conditions
• DV goes on y-axis, shows frequency of amount of each category
• bars are separated to denote that we are dealing with separate conditions

Question 3

when are histograms used?

Answer 3

• when x-axis is continuous (can be divided into smaller categories eg. height) rather than discrete
• bars touching each other shows that x-axis data is continuous

Question 4

what do the x and y-axis represent on a histogram?

Answer 4

• x-axis is made up of equal-sized intervals of a single category
• y-axis represents the frequency within each interval
• if there was a zero frequency for one of the intervals, the interval remains but without a bar

Question 5

when and how do you use scattergrams?

Answer 5

• associations, not differences, between co-variables
• either of the co-variables occupies the x-axis and other the y-axis (doesn’t matter which)
• each point on the graph corresponds to the x and y position of the co-variables

Question 6

when do you use line graphs?

Answer 6

• like histograms, they represent continuous data
• they use points connected by lines to show how something changes in value eg. over time
• IV is x-axis, DV is y-axis

Question 7

describe a normal distribution

Answer 7

• symmetrical bell-shaped curve in which most people occupy the middle area
• mean, median and mode are all at the same central point
• characteristics such as height, weight and IQ are normally distributed in a population

Question 8

what is a positive skew?

Answer 8

• where most of the distribution is concentrated towards the left of the graph, resulting in a longer tail on the right
• mode remains highest point of peak, median comes next but mean is dragged towards the right (because extreme scores affect mean only)
• eg. difficult test where most people got low marks with a handful of students at the higher end

Question 9

what is a negative skew?

Answer 9

• where most of the distribution is concentrated towards the right of the graph, resulting in a longer tail on the left
• mode remains highest point of peak, median comes next but mean is dragged towards the left (because extreme scores affect mean only)
• eg. easy test where most people got high marks with a handful of students at the lower end