# S1 Mindmap

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• S1
• Representing Data
• Types of Variables
• Qualitative: A variable that describes a characteristic
• Quantitative: A variable that can be given a numerical value
• Discrete: Variables that can only take certain values in a given range (Counted)
• Continuous: Variables that can take any value in a given range (Measured)
• Stem and Leaf diagrams
• Neat columns
• Arranged in ascending or descending order
• Draw a key
• Histograms
• Continuous data (no gaps)
• Y axis shows frequency density
• Area = Frequency
• FD = F/CW
• Cumulative Frequency
• Continuous Data
• Graph never decreases
• Maximum graph height = total frequency
• Probability
• Sample Space
• Lists all the possible outcomes of an event, each in a pair of curly brackets
• Exclusivity
• Mutually Exclusive
• Events that CANNOT both happen at the same time
• Non-mutually Exclusive
• Events CAN both happen at the same time
• P(A or B) =   P(A) + P(B) - P(A and B)
• Dependancy
• Events that are independent are when the outcome of one event has no effect on the outcome of another
• Conditional events are when the outcome of one event has an effect on the outcome of another
• P(B given A) = P(A & B)    / P(A)
• Summarising Data
• Measures of Location (Central Tendency)
• Mean
• Sum of values / number of values
• Mid point used if data is grouped
• Easy to calculate
• Makes use of all data
• Can be used in further statistical calculations
• Can be misleading if there is an abnormally high or low value
• Median
• Middle value of an ordered set of data
• Median =   1/2(n+1)th value
• Simple to understand
• Unaffected by abnormally high or low values
• Sometimes is a member of the data set
• Cannot be used in further calculations
• Mode
• Most common value
• 2 modes means it is bi-modal
• Group with highest frequency density is the modal group
• Simple to understand
• Unaffected by abnormally high or low values
• Most useful to producers
• Cannot be used in further calculations
• Cannot be determined exactly in grouped frequency distributions
• Measures of dispersion
• Range
• Largest value - smallest value
• Very limited as it does not consider the pattern of the spread, only the extreme values
• Interquartile range
• Calculates the difference between the upper and lower quartile
• The range of the middle 50% of the distribution
• Box and Whisker plot
• Show lowest, highest values, upper, lower quartiles and median