Chapter 2 Measures of Location and Spread (AS) Flashcards
Mean of ungrouped data
Calculator Mean Screen
Menu -> 6 -> 1
Mean of Frequency Tables
Mean for Grouped Data
Same thing but use midpoints
Mean is affected by…
extreme values
How to find the median of grouped data?
find n/2 then use linear interpolation
Median isn’t affected by..
extreme values
How to find position of the median for listd data?
n/2
- If decimal round up
- If whole, use halfway between this item and the one after
Linear Interpolation Formula
Median = Start Value + Fraction from top x class width of bottom
How to turn items into True Class Limits?
- lower bound minus 0.5
- upper bound plus 0.5
Lower Quartile
1/4 x n
Upper Quartile
3/4 x n
Quartiles
Splits the data up into quarters
Percentiles
Splits the data up into hundredths
Deciles
Splits the data up into tenths
Interquartile Range
Upper Quartile - Lower Quartile
(Q3 - Q1)
What are the three measures of central tendency?
- Mean
- Median
- Mode
What are the other measures of location?
- Miniumum
- Maximum
- Quartiles
- Percentiles
- Deciles
What are the four measures of spread?
- Range
- Interquartile Range
- Standard Deviation
- Variance
Why do we favour the interquartile range over the range?
Because the IQR ignores the extreme values and concentrates on the middle 50%.
Variance takes into account..
all the values (including the extremes)
Variance
Standard Deviation
Other Variance formulae
Summary of coding:
- Measures of LOCATION are affected by ALL parts of coding
- Measures of SPREAD are only affected by multiplicative parts of coding
