RMA - Week 10

density curves

• useful when many pps

• a histogram showing distirubtion of scores of pps

• nromal distribution = …

• increased data points means better curve

• ignores outliers and extreme values

• area of 1 underneath them

positively skewed

sharp peak then long descent of curve

negatively skewed

long ascent then sharp drop

median

point that divides area into equal parts

quartiles

points that divide area under curve into quarters

mode

positions at peak of curve

mean

balancing point of the curve

perfect distribution

mean, median, mode in one place

skewed curves

• Mode stays the same

• Median and mean - skewed psitively/ negatively

• More effect on the mean

usefulness

Because the curve is mathematically defined, you can compare observed data to the normal curve to check how well it fits.

z score

deviation of x from mean / standard deviation

• used to standardise data