Statistics Flashcards
Descriptive statistics
used to describe/summarise the characteristics of a sample or set of data
- such as variables, mean, standard deviation or frequency
MEAN
MoCT
> most sensitive measure- exact distance between all values of data
X distorted by extreme values- less representative
X not NOMINAL data or discrete value (1.7 legs)
MEDIAN
MoCT
- middle value ordered in list
> ORDINAL data can be used
> not affected by extreme scores
X not as sensitive- exact values not reflected because not all data is used
MODE
MoCT
- most frequent occurring value in a set of scores
> discrete data, NOMINAL data can be used, not affected by extreme values
X not useful when there are several modes
RANGE
MoD
- arithmetic distance between top and bottom values
- customary to ADD 1
> identifies how spread out the data is- accounts for end values of data set
> extreme results, can’t see the distribution between numbers
STANDARD DEVIATION
MoD
- measures the spread out of the set of numbers, in effect the average distance of each number from the mean
> precise measure of dispersion
> all values taken into account
> know if the numbers are closely grouped or spread out
> not as affected by extreme results
X may hide characteristics- extreme values- indicates how far each value id rather than looking at values at each end of a data set
NORMAL distribution
BELL CURVE
- mean, median, mode are all in the exacts mid-point
- the distribution is symmetrical around this mid-point
SKEWED distribution
- the mode and the mean are NOT THE SAME SCORE
POSITIVE SKEW - few extreme scores affect mean
- mean always HIGHER than the median and mode
- most scores towards the low end
NEGATIVE SKEW - the mean is BELOW the median and mode
- if marks were plotted for an exam which was very easy so most people got a very high score
50= mean 80= mode
LEFT FOOT NEGATIVE RIGHT FOOT POSITIVE
All graphs need
- a title
- y axis title (DV)
- x axis title (IV)
- plot of graph
Histogram
- data should start from 0
- bars should be touching
- IV is numerical = CONTINUOUS
> interval OR ratio
Line graph
- show information is connected
- change in performance over time
- date must be continuous
Pie chart
- shows FREQUENCY data
- each slice = proportion of category
- total pie is 100%
- NOMINAL data
Scatter diagram
- only for correlations
- paired numerical data want to determine whether 2 co-variables are related
- positive, negative, uncorrelated
Bar chart
- data on the x axis = NOT CONTINUOUS
- usually in categories
- spaces between each bar
- NOMINAL
Frequency table
- may be given table containing raw data
- or MoCT
- mean, median, mode