# Statistics and Probability

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• Maths revision: Statistics and Probability
• Compound Interest and Depreciation
• N = No (1+r/100)^n
• This means: Existing amount = Initial amount (1 + percentage change per day/hour/year) ^ number of days/hrs/yrs/
• Relative frequency
• Probability of something happening = no. of times it happened / no. of times you tried
• The more times you do the experiment, the more accurate the probability is
• Data
• Quantitative = quantities
• Qualitative = descriptive
• Discrete = recorded exactly
• Continuous = take any value in an interval
• Cumulative Frequency
• Means 'Adding it up as you go along'
• Shown in Box Plots
• Histograms
• Its not the height but the area of the bar that matters
• Frequency density = Frequency / Class-width
• Frequency Polygons
• Shows information from a frequency table
• A kind of line graph
• Finding the gradient of a straight line graph
• !) Find two accurate points a complete the triangle
• 2) Find the change in Y and the change in X
• Change in X = X coordinate of point a - X coordinate of point B
• Change in Y = Y coordinate of point A - Y coordinate of point B
• 3) Gradient = Change in Y / Change in X
• Sampling
• Maths revision: Statistics and Probability
• Compound Interest and Depreciation
• N = No (1+r/100)^n
• This means: Existing amount = Initial amount (1 + percentage change per day/hour/year) ^ number of days/hrs/yrs/
• Relative frequency
• Probability of something happening = no. of times it happened / no. of times you tried
• The more times you do the experiment, the more accurate the probability is
• Data
• Quantitative = quantities
• Qualitative = descriptive
• Discrete = recorded exactly
• Continuous = take any value in an interval
• Cumulative Frequency
• Means 'Adding it up as you go along'
• Shown in Box Plots
• Histograms
• Its not the height but the area of the bar that matters
• Frequency density = Frequency / Class-width
• Frequency Polygons
• Shows information from a frequency table
• A kind of line graph
• Finding the gradient of a straight line graph
• !) Find two accurate points a complete the triangle
• 2) Find the change in Y and the change in X
• Change in X = X coordinate of point a - X coordinate of point B
• Change in Y = Y coordinate of point A - Y coordinate of point B
• 3) Gradient = Change in Y / Change in X
• Stratified sampling = makes sure the proportion  of people in each group is the same in the sample as it is in the whole population.
• Sample frame = list/map of all the members of the population
• Population = group you want to investigate
• Quartiles and interquartile range
• Quartiles divide data into four equal groups
• Lower quartile (Q1)
• Median (Q2)
• Upper quartile (Q3)
• To find Quartiles
• 1) Put the values in ASCENDING order
• 2) Work out the quartiles using the following formulas:
• Q1 = (n+1)/4
• Q2 = 2(n+1)/4
• Q3 = 3(n+1)/4
• Interquartile = 'Between Quartiles'
• Interquartile range is the difference between the upper and lower quartile
• To find Quartiles
• 1) Put the values in ASCENDING order
• 2) Work out the quartiles using the following formulas:
• Q1 = (n+1)/4
• Q2 = 2(n+1)/4
• Q3 = 3(n+1)/4
• Interquartile = 'Between Quartiles'
• Interquartile range is the difference between the upper and lower quartile
• Frequency Tables
• Mean is found using: 3rd Row total/2nd Row total
• Median found from middle value in 2nd row
• Range found from extremes of the first row