# Numerical Measures Notes (simple!!) eg mode, median, IQR - Statistics - S1 - AQA - A Level

easy methods to find the mode, median, range, iqr

AQA S1

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• Created on: 30-04-12 22:05

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Statistics - Numerical Measures
Calculating Averages
Mode - simply find the value which occurs the most, non calculator
Median - put values into order and cross off outer values, working your way towards the middle, non
calculator. If there are two middle values, add them together and divide by 2. Tip - can be given
unknown values, but the shouldn't affect median if they are extreme
The median is:
n+1
Odd number of values? 2 th term
n n
Even number of values? it is the average of the 2 th and 2 + 1 th terms
Mean - it is the sum of the values, divided by the number of the values. Type all the values into the x
column in the table in your calculator, type 1 in the frequency column and then find your mean, x.
Easy
Calculating Measures of spread
Range - simply the difference between the highest and lowest values
Interquartile range - is the difference between the upper and lower quartiles. Find the median, then
find the median of both sides (left and right.) Q3 - Q1 = IQR
If you're reading data off a table, then these are the formulas you need:
Q1 = n+1 th term
4
Q2 = n+1 th term
2
3(n+1)
Q3 = 4 th term
Standard deviation - is a measure of the average deviation of values from their mean. Should never
be negative because it is based on the sum of squares. Type all the values into your x column in your
calculator and type 1 into your frequency column, then find the standard deviation, x n-1
Variance - is standard deviation squared
Frequency distribution - use the same method as standard deviation, but enter the correct values
into the frequency column
Estimating (only applies to grouped frequency distribution)

## Other pages in this set

### Page 2

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Mean - need to make a midpoint column and write the midpoint of each class. Enter the midpoint
values into your x column in your calculator and your frequency values into the frequency column. Find
mean button, x
Standard deviation - use same method but press standard deviation button at the end, x
n-1
Linear scaling
Used when converting units.…read more

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