What is an avergae?
A measure of central tendency
How do we calculate the median when the total number of values is odd?
median = (n+1)/2
How do we calculate an ESTIMATE for the median of a histogram?
L + ((n/2) x F)/f x w
where:
- L = lower boundary of median class
- n = total number of values
- F = cumulative frequency of intervals before median class
- f = frequency of median class
- w = width of median class
How do we calculate an estimate for the mean of grouped data?
mean = Σ(f x midpoint)/ Σf
Why do we transform data?
To make calculating averages more manageable
How do we transform data?
De/Increasing all the data values by the same amount, calculate the average, then add/subtract the same amount
What is the formula for the weighted mean?
Weighted mean = Σ(value x weight)/Σweight
What is the formula for the geometric mean?
For n numbers : multiply them all and take the nth root e.g. for 3 numbers, multiply together and take the cube root
What are the advantages of the mode?
- Easy to find
- Can be used with any data
- Unaffected by extreme values
- Is always a data value
What are the disadvantages of the mode?
- May be no mode or several modes
2. Can be used to find a measure of spread`
What are the advantages of the median?
- Easy to calculate
- Good for when the data is skewed
- Unaffected by extreme values
- Can be used to find quartiles and IQR
What are the disadvantags of the median?
May not be a data value
What are the advantages of the mean?
- Uses all the data
2. Can be used to calculate standard deviation and skew
What are the disadvantages of the mean?
- Always affected by extreme values
2. Can be distorted by open-ended classes
